My New Company: Janky A## Solutions, Inc. applications now being accepted.

[CJ Taylor]

Alright before I get started, first of all, this is a help article. I'm
just shocked I didn't think of a solution or couldn't find one on the web at
all. So I figured I would write a quick blurb on here, in someone wants to
post it on there blog so it can be spidered, feel free. I don't have one
yet, should probably set one up.

Alright... Now I brought this issue up a few weeks ago and kinda put it to
the way side but now it has become an issue again with an application I am
developing. I believe Armin was looking for a solution as well, and had
one, but we both agreed it was a bit rough. Well sorta... I use the same
idea, just a little different. And maybe if its written out people will
understand.

Now... what the hell am I talking about? The infamous <select none> inside
a databound combo box. how many times have you been annoyed by a
non-required field but dot net doesn't support adding items to databound
list controls!

So, my fine friends this is a quick and dirty way to do it, which I'll
explain on the way (its not long). And hopefully it will help everyone out.

Alright, a little info about ComboBox. 1, its not as dumb as we all
thought, in fact, its quite ingenious (well, databinding in dot net itself
is pretty cool, this just makes it better). Combobox only cares about 2
interfaces in binding (much like most things) IList, or IListSource.

So knowing this, and knowing the the massive amount of classes that probably
implement IList we can start coming to conculsions.

In my example, we are going to use System.Data.DataTable class for our IList
provider. And use a DataRow as our Object to add to the IList/IListSource
Collection. I find these to be the easiest ones because everything is
implemented as needed (you could roll your own, but in the end, your going
to basically come up with a datarow with less properties/methods. It's up
to you)

The important thing to remember is, Combobox cares about 2 things (as do
you) the DisplayMember and the ValueMember. These are pulled from
Properties within our list source by the combobox. In our case, they
represent the fields of the datarow, or a property of the indexer on IList
(i.e. IList(0)("fieldName"))

So we declare a untyped datarow, and datatable

Dim dr as DataRow
Dim dt as new DataTable("MyTable")

the name of the table isn't important here, I do it out of habit.

Then, add your columns to the datatable for the combobox to bind onto.

dt.Columns.Add(New DataColumn("DisplayMember", getType(String)))
dt.Columns.Add(New DataColumn("ValueMember", getType(Integer)))

Datatypes aren't really important on the valuemember since it can be an
object (rmember though, if it is an object and you wanted to use
SelectedValue you have to implement IComparable)

First, we are going to go ahead and add in our "none" row.

dr = dt.NewRow()
dr("DisplayMember") = "< none ... >"
dr("ValueMember") = 0
dt.Rows.Add(dr)

this adds our first row to the table, obviously not bound to a dataset or
any adapter, so no update worries. I then take the dataset I want data off
of to load into the combobox and load it into my table

Dim cRow as DataRow

for each cRow in myDataSet.Tables("yourTableHere")
dr = dt.NewRow()
dr("DisplayMember") = cRow("PropertyName")
dr("ValueMember") = cRow("OtherPropertyName")
dt.Rows.Add (dr)
next

Finally, bind your source to your combobox.

me.myComboBox.DataSource = dt
me.myComboBox.DisplayMember = "DisplayMember"
me.myComboBox.ValueMember = "ValueMember"

Obviously, you can replace DisplayMember and ValueMember vlaues with
whatever you want, but this is just an example. And thats it. You will be
bound and ready.

A little janky, but it gets the job done with no questions.

Hope it helps.

CJ

 

[One Handed Man [ OHM# ]]

I'm sure ive missed something here as I have a hangover from last night
but what happens when you do a DataAdapter.Update( Your DT )?

OHM

 

[CJ Taylor]

Thats the point... you dont.

=)

I'm sure ive missed something here as I have a hangover from last night
but what happens when you do a DataAdapter.Update( Your DT )?

OHM

 

[CJ Taylor]

or... add .AcceptChanges on the <none> data row. =)

 

[One Handed Man [ OHM# ]]

Hmm, doesent this slow things down a tad ?

As far as I remember, I think I managed to get around this by checking for a
updat event on the datatable or some such event and then inserting the
<Select Value> in the front of the ComboBox each time.

Mind you, its a bit hazy now.

Regards - OHM

 

[Cor]

I'm sure ive missed something here as I have a hangover from last night

but what happens when you do a DataAdapter.Update( Your DT )?

OHM

Is that the reason, I was just thinking before reading this message "what is
that OHM super active this day".

Before you write it, you are of course always active only today super
active.

)

Cor

 

[CJ Taylor]

What??

The bloody dutch...

=)

Nothin' but love for ya.

Plutonically...

 

[CJ Taylor]

And this handled the None issue? Forgive me I just don't see where your
going with this.

I understand your hazy, so that could be the reason. =)

 

[One Handed Man [ OHM# ]]

Sorry, I meant None.

I think that the way I dealt with this was to bind it normally to a dataset
with all the normal DataAdapter stuff, but obviously when your NONE
disapears. I got around this I think by inserting the NONE at the top after
the dataset was updated.

Is that a littler clearer now ?

And this handled the None issue? Forgive me I just don't see where
your going with this.

I understand your hazy, so that could be the reason. =)

Hmm, doesent this slow things down a tad ?

As far as I remember, I think I managed to get around this by
checking for a updat event on the datatable or some such event and
then inserting the <Select Value> in the front of the ComboBox each
time.

Mind you, its a bit hazy now.

Regards - OHM

Thats the point... you dont.

=)

"One Handed Man [ OHM# ]" <O_H_M{at}BTInternet{dot}com> wrote in
message I'm sure ive missed something here as I have a hangover from last
night but what happens when you do a DataAdapter.Update( Your DT )?

OHM

CJ Taylor wrote:
Alright before I get started, first of all, this is a help
article. I'm just shocked I didn't think of a solution or
couldn't find one on the web at all. So I figured I would write
a quick blurb on here, in someone wants to post it on there blog
so it can be spidered, feel free. I don't have one yet, should
probably set one up.

Alright... Now I brought this issue up a few weeks ago and kinda
put it to the way side but now it has become an issue again with
an application I am developing. I believe Armin was looking for a
solution as well, and had one, but we both agreed it was a bit
rough. Well sorta... I use the same idea, just a little
different. And maybe if its written out people will understand.

Now... what the hell am I talking about? The infamous <select
none> inside a databound combo box. how many times have you been
annoyed by a non-required field but dot net doesn't support
adding items to databound list controls!

So, my fine friends this is a quick and dirty way to do it, which
I'll explain on the way (its not long). And hopefully it will
help everyone out.

Alright, a little info about ComboBox. 1, its not as dumb as we
all thought, in fact, its quite ingenious (well, databinding in
dot net itself is pretty cool, this just makes it better).
Combobox only cares about 2 interfaces in binding (much like most
things) IList, or IListSource.

So knowing this, and knowing the the massive amount of classes
that probably implement IList we can start coming to conculsions.

In my example, we are going to use System.Data.DataTable class for
our IList provider. And use a DataRow as our Object to add to the
IList/IListSource Collection. I find these to be the easiest ones
because everything is implemented as needed (you could roll your
own, but in the end, your going to basically come up with a
datarow with less properties/methods. It's up to you)

The important thing to remember is, Combobox cares about 2 things
(as do you) the DisplayMember and the ValueMember. These are
pulled from Properties within our list source by the combobox. In
our case, they represent the fields of the datarow, or a property
of the indexer on IList (i.e. IList(0)("fieldName"))

So we declare a untyped datarow, and datatable

Dim dr as DataRow
Dim dt as new DataTable("MyTable")

the name of the table isn't important here, I do it out of habit.

Then, add your columns to the datatable for the combobox to bind
onto.

dt.Columns.Add(New DataColumn("DisplayMember", getType(String)))
dt.Columns.Add(New DataColumn("ValueMember", getType(Integer)))

Datatypes aren't really important on the valuemember since it can
be an object (rmember though, if it is an object and you wanted
to use SelectedValue you have to implement IComparable)

First, we are going to go ahead and add in our "none" row.

dr = dt.NewRow()
dr("DisplayMember") = "< none ... >"
dr("ValueMember") = 0
dt.Rows.Add(dr)

this adds our first row to the table, obviously not bound to a
dataset or any adapter, so no update worries. I then take the
dataset I want data off of to load into the combobox and load it
into my table

Dim cRow as DataRow

for each cRow in myDataSet.Tables("yourTableHere")
dr = dt.NewRow()
dr("DisplayMember") = cRow("PropertyName")
dr("ValueMember") = cRow("OtherPropertyName")
dt.Rows.Add (dr)
next

Finally, bind your source to your combobox.

me.myComboBox.DataSource = dt
me.myComboBox.DisplayMember = "DisplayMember"
me.myComboBox.ValueMember = "ValueMember"

Obviously, you can replace DisplayMember and ValueMember vlaues
with whatever you want, but this is just an example. And thats
it. You will be bound and ready.

A little janky, but it gets the job done with no questions.

Hope it helps.

CJ

 

[CJ Taylor]

By the way,

no one ever said it was a "great" solution.. hence the name janky a$$
solutions.. =)

Your solution would work too as far as I see it, definnatly more OOP
oriented than mine I suppose, or more .NET friendly for that matter. This
just seemed clear at the time. where were you when I asked this question a
few weeks ago? =)

Peace,
CJ

Sorry, I meant None.

I think that the way I dealt with this was to bind it normally to a dataset
with all the normal DataAdapter stuff, but obviously when your NONE
disapears. I got around this I think by inserting the NONE at the top after
the dataset was updated.

Is that a littler clearer now ?

And this handled the None issue? Forgive me I just don't see where
your going with this.

I understand your hazy, so that could be the reason. =)

Hmm, doesent this slow things down a tad ?

As far as I remember, I think I managed to get around this by
checking for a updat event on the datatable or some such event and
then inserting the <Select Value> in the front of the ComboBox each
time.

Mind you, its a bit hazy now.

Regards - OHM






CJ Taylor wrote:
Thats the point... you dont.

=)

"One Handed Man [ OHM# ]" <O_H_M{at}BTInternet{dot}com> wrote in
message I'm sure ive missed something here as I have a hangover from last
night but what happens when you do a DataAdapter.Update( Your DT )?

OHM

CJ Taylor wrote:
Alright before I get started, first of all, this is a help
article. I'm just shocked I didn't think of a solution or
couldn't find one on the web at all. So I figured I would write
a quick blurb on here, in someone wants to post it on there blog
so it can be spidered, feel free. I don't have one yet, should
probably set one up.

Alright... Now I brought this issue up a few weeks ago and kinda
put it to the way side but now it has become an issue again with
an application I am developing. I believe Armin was looking for a
solution as well, and had one, but we both agreed it was a bit
rough. Well sorta... I use the same idea, just a little
different. And maybe if its written out people will understand.

Now... what the hell am I talking about? The infamous <select
none> inside a databound combo box. how many times have you been
annoyed by a non-required field but dot net doesn't support
adding items to databound list controls!

So, my fine friends this is a quick and dirty way to do it, which
I'll explain on the way (its not long). And hopefully it will
help everyone out.

Alright, a little info about ComboBox. 1, its not as dumb as we
all thought, in fact, its quite ingenious (well, databinding in
dot net itself is pretty cool, this just makes it better).
Combobox only cares about 2 interfaces in binding (much like most
things) IList, or IListSource.

So knowing this, and knowing the the massive amount of classes
that probably implement IList we can start coming to conculsions.

In my example, we are going to use System.Data.DataTable class for
our IList provider. And use a DataRow as our Object to add to the
IList/IListSource Collection. I find these to be the easiest ones
because everything is implemented as needed (you could roll your
own, but in the end, your going to basically come up with a
datarow with less properties/methods. It's up to you)

The important thing to remember is, Combobox cares about 2 things
(as do you) the DisplayMember and the ValueMember. These are
pulled from Properties within our list source by the combobox. In
our case, they represent the fields of the datarow, or a property
of the indexer on IList (i.e. IList(0)("fieldName"))

So we declare a untyped datarow, and datatable

Dim dr as DataRow
Dim dt as new DataTable("MyTable")

the name of the table isn't important here, I do it out of habit.

Then, add your columns to the datatable for the combobox to bind
onto.

dt.Columns.Add(New DataColumn("DisplayMember", getType(String)))
dt.Columns.Add(New DataColumn("ValueMember", getType(Integer)))

Datatypes aren't really important on the valuemember since it can
be an object (rmember though, if it is an object and you wanted
to use SelectedValue you have to implement IComparable)

First, we are going to go ahead and add in our "none" row.

dr = dt.NewRow()
dr("DisplayMember") = "< none ... >"
dr("ValueMember") = 0
dt.Rows.Add(dr)

this adds our first row to the table, obviously not bound to a
dataset or any adapter, so no update worries. I then take the
dataset I want data off of to load into the combobox and load it
into my table

Dim cRow as DataRow

for each cRow in myDataSet.Tables("yourTableHere")
dr = dt.NewRow()
dr("DisplayMember") = cRow("PropertyName")
dr("ValueMember") = cRow("OtherPropertyName")
dt.Rows.Add (dr)
next

Finally, bind your source to your combobox.

me.myComboBox.DataSource = dt
me.myComboBox.DisplayMember = "DisplayMember"
me.myComboBox.ValueMember = "ValueMember"

Obviously, you can replace DisplayMember and ValueMember vlaues
with whatever you want, but this is just an example. And thats
it. You will be bound and ready.

A little janky, but it gets the job done with no questions.

Hope it helps.

CJ

 

[Jay B. Harlow [MVP - Outlook]]

CJ,
Why Not??

I would think if you called DataRow.AcceptChanges as CJ suggested on your
"none" row, or used DataRow.Remove before you called Update, the DataAdapter
will be non the wiser. I would expect AcceptChanges to be the "cleaner"
method, while Remove would be the safer method. ;-)

My concern with this technique is "key" conflicts.

Another heavier option would be a DataView wrapper that dynamically added
the row being reported to the listbox, however the DataTable itself would
not contain the actual item. Which would be more code, however it would
avoid the "key" conflicts. A wrapper could keep the "none" row at the top of
the list, even when changing the sort order...

Hope this helps
Jay

 

[One Handed Man [ OHM# ]]

Sorry CJ, I wasn't dumping on your idea's. Its just that I was trying to
help someone here several weeks ago on the same subject and that's the
solution I came up with.

Regards - OHM

By the way,

no one ever said it was a "great" solution.. hence the name janky a$$
solutions.. =)

Your solution would work too as far as I see it, definnatly more OOP
oriented than mine I suppose, or more .NET friendly for that matter.
This just seemed clear at the time. where were you when I asked this
question a few weeks ago? =)

Peace,
CJ

Sorry, I meant None.

I think that the way I dealt with this was to bind it normally to a
dataset with all the normal DataAdapter stuff, but obviously when
your NONE disapears. I got around this I think by inserting the NONE
at the top after the dataset was updated.

Is that a littler clearer now ?

And this handled the None issue? Forgive me I just don't see where
your going with this.

I understand your hazy, so that could be the reason. =)


"One Handed Man [ OHM# ]" <O_H_M{at}BTInternet{dot}com> wrote in
message Hmm, doesent this slow things down a tad ?

As far as I remember, I think I managed to get around this by
checking for a updat event on the datatable or some such event and
then inserting the <Select Value> in the front of the ComboBox each
time.

Mind you, its a bit hazy now.

Regards - OHM






CJ Taylor wrote:
Thats the point... you dont.

=)

"One Handed Man [ OHM# ]" <O_H_M{at}BTInternet{dot}com> wrote in
message I'm sure ive missed something here as I have a hangover from last
night but what happens when you do a DataAdapter.Update( Your DT
)?

OHM

CJ Taylor wrote:
Alright before I get started, first of all, this is a help
article. I'm just shocked I didn't think of a solution or
couldn't find one on the web at all. So I figured I would write
a quick blurb on here, in someone wants to post it on there blog
so it can be spidered, feel free. I don't have one yet, should
probably set one up.

Alright... Now I brought this issue up a few weeks ago and kinda
put it to the way side but now it has become an issue again with
an application I am developing. I believe Armin was looking
for a solution as well, and had one, but we both agreed it was
a bit rough. Well sorta... I use the same idea, just a little
different. And maybe if its written out people will understand.

Now... what the hell am I talking about? The infamous <select
none> inside a databound combo box. how many times have you
been annoyed by a non-required field but dot net doesn't support
adding items to databound list controls!

So, my fine friends this is a quick and dirty way to do it,
which I'll explain on the way (its not long). And hopefully it
will help everyone out.

Alright, a little info about ComboBox. 1, its not as dumb as we
all thought, in fact, its quite ingenious (well, databinding in
dot net itself is pretty cool, this just makes it better).
Combobox only cares about 2 interfaces in binding (much like
most things) IList, or IListSource.

So knowing this, and knowing the the massive amount of classes
that probably implement IList we can start coming to
conculsions.

In my example, we are going to use System.Data.DataTable class
for our IList provider. And use a DataRow as our Object to add
to the IList/IListSource Collection. I find these to be the
easiest ones because everything is implemented as needed (you
could roll your own, but in the end, your going to basically
come up with a datarow with less properties/methods. It's up
to you)

The important thing to remember is, Combobox cares about 2
things (as do you) the DisplayMember and the ValueMember.
These are pulled from Properties within our list source by the
combobox. In our case, they represent the fields of the
datarow, or a property of the indexer on IList (i.e.
IList(0)("fieldName"))

So we declare a untyped datarow, and datatable

Dim dr as DataRow
Dim dt as new DataTable("MyTable")

the name of the table isn't important here, I do it out of
habit.

Then, add your columns to the datatable for the combobox to bind
onto.

dt.Columns.Add(New DataColumn("DisplayMember", getType(String)))
dt.Columns.Add(New DataColumn("ValueMember", getType(Integer)))

Datatypes aren't really important on the valuemember since it
can be an object (rmember though, if it is an object and you
wanted to use SelectedValue you have to implement IComparable)

First, we are going to go ahead and add in our "none" row.

dr = dt.NewRow()
dr("DisplayMember") = "< none ... >"
dr("ValueMember") = 0
dt.Rows.Add(dr)

this adds our first row to the table, obviously not bound to a
dataset or any adapter, so no update worries. I then take the
dataset I want data off of to load into the combobox and load it
into my table

Dim cRow as DataRow

for each cRow in myDataSet.Tables("yourTableHere")
dr = dt.NewRow()
dr("DisplayMember") = cRow("PropertyName")
dr("ValueMember") = cRow("OtherPropertyName")
dt.Rows.Add (dr)
next

Finally, bind your source to your combobox.

me.myComboBox.DataSource = dt
me.myComboBox.DisplayMember = "DisplayMember"
me.myComboBox.ValueMember = "ValueMember"

Obviously, you can replace DisplayMember and ValueMember vlaues
with whatever you want, but this is just an example. And thats
it. You will be bound and ready.

A little janky, but it gets the job done with no questions.

Hope it helps.

CJ

 

[CJ Taylor]

CJ,
Why Not??

I would think if you called DataRow.AcceptChanges as CJ suggested on your
"none" row, or used DataRow.Remove before you called Update, the DataAdapter
will be non the wiser. I would expect AcceptChanges to be the "cleaner"
method, while Remove would be the safer method. ;-)

My concern with this technique is "key" conflicts.

Another heavier option would be a DataView wrapper that dynamically added
the row being reported to the listbox, however the DataTable itself would
not contain the actual item. Which would be more code, however it would
avoid the "key" conflicts. A wrapper could keep the "none" row at the top of
the list, even when changing the sort order...

Wait. How can you add a row to a dataview and not a datatable? Isn't after
all a dataview just some fancy footwork around DataTable.Select() method?
And provide some quick sort capabilities to it as well? So I don't see how
that would work, let me know what I'm missing.

Second of all, with the key conflicts, thats why I suggested the secondary
non-bound table with only 2 fields. Yeah its more code in some cases but
you have more control over your combos. This way, key constraints are not
an issue as they are with strongly typed datasets. You could easily create
a simple method (static if you wished to take in an IList/IListSource
object, a Display Variable and a Value Variable as parameters and easily
create your datatable off that.

I like your idea about keeping none at the top, I just don't now how you
would accomplish this dataview wrapper without being incredibly heavy...

-CJ

 

[CJ Taylor]

Fair enough, I'm not mad at ya. =) I know people have been trying to solve
this thing, I just thought I would throw my hat into the ring.

Obviously, if there is debate here over how to do it, there isn't a "clear"
answer out there. so who is to say who is right or wrong. I, like you are
trying to give a solution to doing it, hopefully, someone will find a better
way. =)

Sorry CJ, I wasn't dumping on your idea's. Its just that I was trying to
help someone here several weeks ago on the same subject and that's the
solution I came up with.

Regards - OHM

By the way,

no one ever said it was a "great" solution.. hence the name janky a$$
solutions.. =)

Your solution would work too as far as I see it, definnatly more OOP
oriented than mine I suppose, or more .NET friendly for that matter.
This just seemed clear at the time. where were you when I asked this
question a few weeks ago? =)

Peace,
CJ

Sorry, I meant None.

I think that the way I dealt with this was to bind it normally to a
dataset with all the normal DataAdapter stuff, but obviously when
your NONE disapears. I got around this I think by inserting the NONE
at the top after the dataset was updated.

Is that a littler clearer now ?





CJ Taylor wrote:
And this handled the None issue? Forgive me I just don't see where
your going with this.

I understand your hazy, so that could be the reason. =)


"One Handed Man [ OHM# ]" <O_H_M{at}BTInternet{dot}com> wrote in
message Hmm, doesent this slow things down a tad ?

As far as I remember, I think I managed to get around this by
checking for a updat event on the datatable or some such event and
then inserting the <Select Value> in the front of the ComboBox each
time.

Mind you, its a bit hazy now.

Regards - OHM






CJ Taylor wrote:
Thats the point... you dont.

=)

"One Handed Man [ OHM# ]" <O_H_M{at}BTInternet{dot}com> wrote in
message I'm sure ive missed something here as I have a hangover from last
night but what happens when you do a DataAdapter.Update( Your DT
)?

OHM

CJ Taylor wrote:
Alright before I get started, first of all, this is a help
article. I'm just shocked I didn't think of a solution or
couldn't find one on the web at all. So I figured I would write
a quick blurb on here, in someone wants to post it on there blog
so it can be spidered, feel free. I don't have one yet, should
probably set one up.

Alright... Now I brought this issue up a few weeks ago and kinda
put it to the way side but now it has become an issue again with
an application I am developing. I believe Armin was looking
for a solution as well, and had one, but we both agreed it was
a bit rough. Well sorta... I use the same idea, just a little
different. And maybe if its written out people will understand.

Now... what the hell am I talking about? The infamous <select
none> inside a databound combo box. how many times have you
been annoyed by a non-required field but dot net doesn't support
adding items to databound list controls!

So, my fine friends this is a quick and dirty way to do it,
which I'll explain on the way (its not long). And hopefully it
will help everyone out.

Alright, a little info about ComboBox. 1, its not as dumb as we
all thought, in fact, its quite ingenious (well, databinding in
dot net itself is pretty cool, this just makes it better).
Combobox only cares about 2 interfaces in binding (much like
most things) IList, or IListSource.

So knowing this, and knowing the the massive amount of classes
that probably implement IList we can start coming to
conculsions.

In my example, we are going to use System.Data.DataTable class
for our IList provider. And use a DataRow as our Object to add
to the IList/IListSource Collection. I find these to be the
easiest ones because everything is implemented as needed (you
could roll your own, but in the end, your going to basically
come up with a datarow with less properties/methods. It's up
to you)

The important thing to remember is, Combobox cares about 2
things (as do you) the DisplayMember and the ValueMember.
These are pulled from Properties within our list source by the
combobox. In our case, they represent the fields of the
datarow, or a property of the indexer on IList (i.e.
IList(0)("fieldName"))

So we declare a untyped datarow, and datatable

Dim dr as DataRow
Dim dt as new DataTable("MyTable")

the name of the table isn't important here, I do it out of
habit.

Then, add your columns to the datatable for the combobox to bind
onto.

dt.Columns.Add(New DataColumn("DisplayMember", getType(String)))
dt.Columns.Add(New DataColumn("ValueMember", getType(Integer)))

Datatypes aren't really important on the valuemember since it
can be an object (rmember though, if it is an object and you
wanted to use SelectedValue you have to implement IComparable)

First, we are going to go ahead and add in our "none" row.

dr = dt.NewRow()
dr("DisplayMember") = "< none ... >"
dr("ValueMember") = 0
dt.Rows.Add(dr)

this adds our first row to the table, obviously not bound to a
dataset or any adapter, so no update worries. I then take the
dataset I want data off of to load into the combobox and load it
into my table

Dim cRow as DataRow

for each cRow in myDataSet.Tables("yourTableHere")
dr = dt.NewRow()
dr("DisplayMember") = cRow("PropertyName")
dr("ValueMember") = cRow("OtherPropertyName")
dt.Rows.Add (dr)
next

Finally, bind your source to your combobox.

me.myComboBox.DataSource = dt
me.myComboBox.DisplayMember = "DisplayMember"
me.myComboBox.ValueMember = "ValueMember"

Obviously, you can replace DisplayMember and ValueMember vlaues
with whatever you want, but this is just an example. And thats
it. You will be bound and ready.

A little janky, but it gets the job done with no questions.

Hope it helps.

CJ

 

[Jay B. Harlow [MVP - Outlook]]

CJ,

Wait. How can you add a row to a dataview and not a datatable? Isn't after


I like your idea about keeping none at the top, I just don't now how you
would accomplish this dataview wrapper without being incredibly heavy...

Notice that I stated HEAVY and WRAPPER!

I was suggesting using the Proxy Pattern to create a DataView *like* object
that always returned "<none>" for the very first element, otherwise it
returned the actual value of a contained DataView. Any changes to the
contained DataView would be reflected in the DataView *like* object...

A start of such a class might be:

Public Class MyDataView
Implements IBindingList
Implements ISupportInitialize
Implements ITypedList

Private Readonly m_view As DataView

Public Sub New(Byval view As DataView)
m_view = view
End Sub

' Helper property
Protected Readonly Property List() As IList
Get
Return DirectCast(m_view, IList)
End Get
End Property

Public Readonly Count() As Integer Implements ICollection.Count
Get
Return List.Count + 1
End Get
End Property

Default Public Readonly Property Item(ByVal index As Integer) As
DataRowView
Get
Return DirectCast(IList_Item(index) , DataRowView)
End Get
End Property

Private Property IList_Item(ByVal index As Integer) As Object
Implements System.Collections.IList.Item
Get
If index = 0 Then
Return "<none>"
Else
Return List.Item(index - 1)
End If
End Get
Set(ByVal value As Object)
List.Item(index - 1) = value
End Set
End Property

...

End Class

Of course you need to do more work then I show as the DataView returns
DataRowView objects and my IList_Item is attempting to return a string...
Hint DataRowView is not publicly createable I would consider returning
IEditableObject or ICustomTypeDescriptor in the proxy class... then had a
"nop" IEditableObject implementation for None.

I would probably hide most of the implemented methods and expose ones
similar to how the DataView itself does it, as I show with the Item
property.

Of course this DataView *like* class may be more pain then gain, but I
suspect anyone implementing it would have a greater understanding of how
Databinding works ;-)

Second of all, with the key conflicts, thats why I suggested the secondary

Missed that part :-(

Hope this helps
Jay

top

Wait. How can you add a row to a dataview and not a datatable? Isn't after
all a dataview just some fancy footwork around DataTable.Select() method?
And provide some quick sort capabilities to it as well? So I don't see how
that would work, let me know what I'm missing.

Second of all, with the key conflicts, thats why I suggested the secondary
non-bound table with only 2 fields. Yeah its more code in some cases but
you have more control over your combos. This way, key constraints are not
an issue as they are with strongly typed datasets. You could easily create
a simple method (static if you wished to take in an IList/IListSource
object, a Display Variable and a Value Variable as parameters and easily
create your datatable off that.

I like your idea about keeping none at the top, I just don't now how you
would accomplish this dataview wrapper without being incredibly heavy...

-CJ

<<snip>>

 

[Cor]

HI CJ and Jay B.

This was a problem in the ADONET newsgroup. I changed the sample some
minutes ago totaly I did use the northwind database and a dataset and now
it is a datable.

And Jay B is involved so I have to do it right after my acceptchanges

This is the start of the text of a combobox

A ComboBox displays an editing field combined with a ListBox, allowing the
user to select from the list or to enter new text.

I got it as this far, but maybe you can tell what is wrong.
Not the easy answers they are given already.

It is totaly testable, needs only a textbox and a combobox on a form.

Cor

\\\
Private dv As New DataView
Dim bool As Boolean
Private Sub Form1_Load(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
Dim dt As New DataTable
dt.Columns.Add("A")
For i As Integer = 0 To 50
dt.Rows.Add(dt.NewRow)
dt.Rows(i)(0) = i.ToString
Next
Me.ComboBox1.BeginUpdate()
dv = New DataView(dt)
'-------------------------------------------------------------
'DOES NOT WORK
'Me.ComboBox1.DataBindings.Add(New Binding("Text", dv, "A"))
'THIS WORKS FINE
Me.TextBox1.DataBindings.Add(New Binding("Text", dv, "A"))
'---------------------------------------------------------------
Me.ComboBox1.DataSource = dv
Me.ComboBox1.DisplayMember = "A"
Me.ComboBox1.ValueMember = "A"
Me.ComboBox1.EndUpdate()
bool = True
End Sub
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
If bool Then
DirectCast(BindingContext(dv), CurrencyManager).EndCurrentEdit()
End If
End Sub
///

 

[CJ Taylor]

Hey Cor,

HI CJ and Jay B.

This was a problem in the ADONET newsgroup. I changed the sample some
minutes ago totaly I did use the northwind database and a dataset and now
it is a datable.

And Jay B is involved so I have to do it right after my acceptchanges

This is the start of the text of a combobox

A ComboBox displays an editing field combined with a ListBox, allowing the
user to select from the list or to enter new text.

I got it as this far, but maybe you can tell what is wrong.
Not the easy answers they are given already.

It is totaly testable, needs only a textbox and a combobox on a form.

Cor

\\\
Private dv As New DataView
Dim bool As Boolean
Private Sub Form1_Load(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
Dim dt As New DataTable
dt.Columns.Add("A")
For i As Integer = 0 To 50
dt.Rows.Add(dt.NewRow)
dt.Rows(i)(0) = i.ToString
Next
Me.ComboBox1.BeginUpdate()
dv = New DataView(dt)
'-------------------------------------------------------------
'DOES NOT WORK
'Me.ComboBox1.DataBindings.Add(New Binding("Text", dv, "A"))

I ran into the same problem this morning (while I sheepishly retreated to my
"drawing board". I did get it to work if I assigned the databinding AFTER I
set the datasource/datamember and the display and value members.

Why, I'm not really sure, but it worked. i don't like that... Try it out
and tell me if you get the same result.

 

[Cor]

Hi CJ,

This gives another behaviour (I even forgot it), than with me it goes
copying the previous selection on the place of the changed selection. (Or
something so watch what you are doing)

Cor