Null Dates in Dataset

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Guest

Using C# 2.0 & SQL Server 2000, have a stored procedure that return 0, 1, or
more rows. At least one of the columns is a date and it may null. I have
created an XSD of the output from the stored proc. The entry for the
nullable date column is "<xs:element name="Sent_Dttm" minOccurs="0"
type="xs:dateTime" nillable="true"></xs:element>". I copied the XSD to the
C# 2.0 windows app I am developing and it nicely generates a strongly typed
dataset.

The problem is I get an error when attempting to access this column in the
dataset when the value is null:
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public System.DateTime Sent_Dttm {
get {
try {
return
((System.DateTime)(this[this.tableOwizCommDoc.Sent_DttmColumn]));
}
catch (System.InvalidCastException e) {
throw new System.Data.StrongTypingException("The
value for column \'Sent_Dttm\' in table \'OwizCommDoc\' is DBNull.", e);
}
}
set {
this[this.tableOwizCommDoc.Sent_DttmColumn] = value;
}
}


Checking the properties of this field, I noticed that the "NullValue"
property has a value of "(throw exception)'
 
Using C# 2.0 & SQL Server 2000, have a stored procedure that return 0, 1, or
more rows. At least one of the columns is a date and it may null. I have
created an XSD of the output from the stored proc. The entry for the
nullable date column is "<xs:element name="Sent_Dttm" minOccurs="0"
type="xs:dateTime" nillable="true"></xs:element>". I copied the XSD to the
C# 2.0 windows app I am developing and it nicely generates a strongly typed
dataset.

The problem is I get an error when attempting to access this column in the
dataset when the value is null:
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public System.DateTime Sent_Dttm {
get {
try {
return
((System.DateTime)(this[this.tableOwizCommDoc.Sent_DttmColumn]));
}
catch (System.InvalidCastException e) {
throw new System.Data.StrongTypingException("The
value for column \'Sent_Dttm\' in table \'OwizCommDoc\' is DBNull.", e);
}
}
set {
this[this.tableOwizCommDoc.Sent_DttmColumn] = value;
}
}


Checking the properties of this field, I noticed that the "NullValue"
property has a value of "(throw exception)'
Click to expand...

Robert,
Try checking for System.DbNull before accessing the variable and that
should help you out.
 
This is by design. The strongly typed dataset will have a method (not
property) IsSent_DttmNull() if the underlying column can be null.

if (!IsSent_DttmNull) {access the value}

Rachel Appel said:
Using C# 2.0 & SQL Server 2000, have a stored procedure that return 0, 1,
or
more rows. At least one of the columns is a date and it may null. I
have
created an XSD of the output from the stored proc. The entry for the
nullable date column is "<xs:element name="Sent_Dttm" minOccurs="0"
type="xs:dateTime" nillable="true"></xs:element>". I copied the XSD to
the
C# 2.0 windows app I am developing and it nicely generates a strongly
typed
dataset.

The problem is I get an error when attempting to access this column in
the
dataset when the value is null:
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public System.DateTime Sent_Dttm {
get {
try {
return
((System.DateTime)(this[this.tableOwizCommDoc.Sent_DttmColumn]));
}
catch (System.InvalidCastException e) {
throw new System.Data.StrongTypingException("The
value for column \'Sent_Dttm\' in table \'OwizCommDoc\' is DBNull.", e);
}
}
set {
this[this.tableOwizCommDoc.Sent_DttmColumn] = value;
}
}


Checking the properties of this field, I noticed that the "NullValue"
property has a value of "(throw exception)'
Click to expand...

Robert,
Try checking for System.DbNull before accessing the variable and that
should help you out.
Click to expand...
 
The issue is that I'm getting bounced in a section of the code automatically
generated when I add an XSD file to the project. If I start going in and
changing generated code than I am defeating the advance of the code
generation.

I was hoping that there was a way of influencing the code generation. Is
there?

Jim Rand said:
This is by design. The strongly typed dataset will have a method (not
property) IsSent_DttmNull() if the underlying column can be null.

if (!IsSent_DttmNull) {access the value}

Rachel Appel said:
Using C# 2.0 & SQL Server 2000, have a stored procedure that return 0, 1,
or
more rows. At least one of the columns is a date and it may null. I
have
created an XSD of the output from the stored proc. The entry for the
nullable date column is "<xs:element name="Sent_Dttm" minOccurs="0"
type="xs:dateTime" nillable="true"></xs:element>". I copied the XSD to
the
C# 2.0 windows app I am developing and it nicely generates a strongly
typed
dataset.

The problem is I get an error when attempting to access this column in
the
dataset when the value is null:
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public System.DateTime Sent_Dttm {
get {
try {
return
((System.DateTime)(this[this.tableOwizCommDoc.Sent_DttmColumn]));
}
catch (System.InvalidCastException e) {
throw new System.Data.StrongTypingException("The
value for column \'Sent_Dttm\' in table \'OwizCommDoc\' is DBNull.", e);
}
}
set {
this[this.tableOwizCommDoc.Sent_DttmColumn] = value;
}
}


Checking the properties of this field, I noticed that the "NullValue"
property has a value of "(throw exception)'
Click to expand...

Robert,
Try checking for System.DbNull before accessing the variable and that
should help you out.
Click to expand...
Click to expand...
 
Robert,

If a column allows nulls, then there is in your strongly typed dataset
created a method named as IsTheFieldNameNull()

If the DataBase does not allows Nulls, then it is of course a normal error.

Cor
 
As I pointed out earlier, the error is occurring in code generated when I
copied an XSD file to my C# 2.0 project. The line of code that I manually
generated is "ds.Load(rdr, LoadOption.OverwriteChanges, new String[] {
"OwizCommFaxDoc" });" where ds has been defined as an instance of the
strongly typed dataset.

The line from the XSD that defines the offending column is "<xs:element
name="Sent_Dttm" minOccurs="0" type="xs:dateTime"
nillable="true"></xs:element>
" minOccurs="1" type="xs:string"></xs:element>
 
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