chnage the Array Element

[sh]

Hi All..

i am Writing a C# code ..but i had face a small problem ,
i hope that you can solve it Please.

I had creat the following class

class Q
{
int A;
Int B
}

then in the main i creat an array of the above class

Q[] Array_Q = new Q[55]();

then i tried to fill the elemnets with a values

int i,j;
for (i=0 ; i<=10 ; i++)
{
for (j=i;j<=10;j++)
Array_Q.A = i; //<== here is the error
Array_Q.B = j;
}


if I run the program it give me an Exchption handelling
Error ..!!
so what is the Problem do you think..


thank you All

 

[Jon Skeet]

then in the main i creat an array of the above class

Q[] Array_Q = new Q[55]();

That creates an array of references, all of which are null to start
with. It doesn't create a single instance of Q. You need to change the
element to refer to a valid instance before doing anything else.

then i tried to fill the elemnets with a values

int i,j;
for (i=0 ; i<=10 ; i++)
{
for (j=i;j<=10;j++)

Put in: Array_Q = new Q(); and it will work

Array_Q.A = i; //<== here is the error
Array_Q.B = j;
}

<snip>

It's very important to know the difference between reference types and
value types - if Q had been a value type, it would have worked. See
http://www.pobox.com/~skeet/csharp/parameters.html and
http://www.pobox.com/~skeet/csharp/memory.html

 

[sh]

Ok .. thank you Mr.Jon Skeet
I will try it ... and I will see

Thank you agin

-----Original Message-----

then in the main i creat an array of the above class

Q[] Array_Q = new Q[55]();

That creates an array of references, all of which are null to start
with. It doesn't create a single instance of Q. You need to change the
element to refer to a valid instance before doing anything else.

then i tried to fill the elemnets with a values

int i,j;
for (i=0 ; i<=10 ; i++)
{
for (j=i;j<=10;j++)

Put in: Array_Q = new Q(); and it will work

Array_Q.A = i; //<== here is the error
Array_Q.B = j;
}

<snip>

It's very important to know the difference between reference types and
value types - if Q had been a value type, it would have worked. See
http://www.pobox.com/~skeet/csharp/parameters.html and
http://www.pobox.com/~skeet/csharp/memory.html

--
Jon Skeet - <[email protected]>
http://www.pobox.com/~skeet/
If replying to the group, please do not mail me too
.

 

[David Lau]

Thanks, it is very useful for the beginner like me

Ok .. thank you Mr.Jon Skeet
I will try it ... and I will see

Thank you agin

-----Original Message-----

then in the main i creat an array of the above class

Q[] Array_Q = new Q[55]();

That creates an array of references, all of which are null to start
with. It doesn't create a single instance of Q. You need to change the
element to refer to a valid instance before doing anything else.

then i tried to fill the elemnets with a values

int i,j;
for (i=0 ; i<=10 ; i++)
{
for (j=i;j<=10;j++)

Put in: Array_Q = new Q(); and it will work

Array_Q.A = i; //<== here is the error
Array_Q.B = j;
}

<snip>

It's very important to know the difference between reference types and
value types - if Q had been a value type, it would have worked. See
http://www.pobox.com/~skeet/csharp/parameters.html and
http://www.pobox.com/~skeet/csharp/memory.html

--
Jon Skeet - <[email protected]>
http://www.pobox.com/~skeet/
If replying to the group, please do not mail me too
.