aspxgridview, object reference not set to an instance of an object

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I created a user control contain aspxgridview and page contain this user control and button when i click on the button in the page i pass values to methods in my user control
this code in the page pass values to method in user control

C#

protected void ASPxButton1_Click(object sender, EventArgs e)
        {
            DisplayAttachmentControl d = new DisplayAttachmentControl();
            d.DisplayData(5, null);
        }

this is the method in my user control

C#

public void DisplayData(int? documentId, int? ticketId)
        {
            Attachments attachment = new Attachments();
            dt = attachment.GetAttachmentByDocumentIDorTicketID(documentId, null);
 
            ASPxGridView1.DataSource = dt;
            ASPxGridView1.DataBind();
        }

the problem is when i pass datatable to aspxgridview1 this error appear

System.NullReferenceException: Object reference not set to an instance of an object.

Posted 30-Aug-15 21:50pm

tranesyasd

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OriginalGriff · Answer 1 · 2015-08-30T22:58:00

Solution 1

Start by looking at your GetAttachmentByDocumentIDorTicketID method: I'm just guessing that it doesn't find any matching values and as a result it doesn't return a DataTable.

Use the debugger, and check what it returns - if it's null, then you need to step into your method and work out why.
We can;t do that for you - we don't have any access to your code or data, and can;t run you application!

Posted 30-Aug-15 22:58pm

OriginalGriff

Comments

tranesyasd 31-Aug-15 5:09am

the datatable return value the problem is when i use the grid in the method it be null i donot know why?

OriginalGriff 31-Aug-15 5:27am

We can't tell you what to do - you need to look yourself (we can't access your HDD!)
So which value is null, and which line it the error reported on.
Use the debugger, and tell us.

tranesyasd 31-Aug-15 5:10am

i tried to use my grid using findcontrol method the same error appear

tranesyasd 31-Aug-15 5:33am

when i used debugger every thing ok and dt returned rows
when i reach the line
ASPxGridView1.DataSource = dt;
the ASPxGridView1 is null
i think its null because i access it from another page

OriginalGriff 31-Aug-15 5:58am

You can't access a GridView on a different page!

What are you trying to do, exactly?

tranesyasd 31-Aug-15 5:42am

also if i only bind the aspxgridview1 it be null also

tranesyasd 31-Aug-15 6:22am

i create user control contain aspxgridview
i will use this user control in my page in the code behind of this page i will get the id and pass it to the grid in the user control to fill the data and display it

this i want to do

OriginalGriff 31-Aug-15 6:47am

So pass it to the instance of the usercontrol and let it decide what to do with it - don't try to access the user control internals from the page code!
Use a property or method of the control instance.

tranesyasd 1-Sep-15 1:41am

i passed the value using method and i filled the datatable depending on this value ,the problem when i bind the grid it be null

tranesyasd 1-Sep-15 3:51am

i solved it
thank you