ASP.NET Gridview - Dynamic in code - non-null data table as Source - DataBind throws Exception

Question

C# ASP.Net 4.7.2

I am creating a Gridview in code based on the dataSet passed in. I create the BoundFields on the fly, and then I assign the DataSource and attempt a DataBind. This code is in a separate class. to which I pass in a placeholder from a page.

Here is the code:

    DGWorkWith = new GridView()
    {
        AllowPaging = true,
        AllowSorting = true,
        PageSize = 50,
        AutoGenerateColumns = false,
        BorderColor = Color.Black,
        BorderWidth = 1
    };
    DataSet wwDS = LoadDataSet(_sDB,_sPW);
    DataTable wwDT = wwDS.Tables[0];
    foreach (DataColumn DC in wwDT.Columns)
    {
        string sColName = DC.ColumnName.ToUpper().Trim();
        string sWidth = myRM.GetString(sColName + "_WIDTH");
        if (sWidth == null) { sWidth = "120"; }
        int iWidth = Convert.ToInt32(sWidth);
        //if (IsFieldChooserColumnOn(sColName)) { continue; }
        // Put DataColumn in List
        string sColHdr = "";
        if (myRM.GetString(sColName) == null)
        {
            sColHdr = "???-" + DC.ColumnName.ToUpper().Trim();
        }
        else
        {
            sColHdr = myRM.GetString(sColName);
        }

        BoundField BC = new BoundField();
        BC.DataField = DC.ColumnName.Trim();
        BC.HeaderText = sColHdr;
        if(iWidth==0) { BC.Visible = false;  }
        DGWorkWith.Columns.Add(BC);
    }
    DGWorkWith.DataSource = wwDT;
    // *** THIS DATABIND FAILS with an Object reference not set to an instance of an object.
    DGWorkWith.DataBind();
    TR2TC2.Controls.Add(DGWorkWith);
    
    TR2.Cells.Add(TR2TC2);
    T.Rows.Add(TR2);
    placeHolder.Controls.Add(T); //T is a Table and the placeholder is fed the table.

The DataBind call fails with the null object reference exception.

DGWorkWith is not Null
The columns are all present for every data column in the DataTable
The column names in the BoundFields match the ColumnNames in the DataTable.
There are rows in the DataTable -- over 12000 of them.
Attempting to step into the DataBind throws the exception at once.

I am completely perplexed.

Does anyone see something I have missed?

Thanks! John.

Whatever I try, the code works. I'm unable to reproduce the problem... Are you sure the problem is not somewhere else since you can bind null to a GridView (DGWorkWith.DataSource = null; shows an empty GridView) — VDWWD
– VDWWD, Commented Sep 25, 2020 at 22:55
I can bind null to the gridview and it shows nothing but not the DataTable. -- which has columns and rows and where every column name matches a column name in the dataTable. — John Tamburo
– John Tamburo, Commented Sep 26, 2020 at 15:38

John Tamburo · Accepted Answer · 2020-09-26 16:44:38Z

0

I found the problem. It was in this code here:

TR2TC2.Controls.Add(DGWorkWith);

TR2.Cells.Add(TR2TC2);
T.Rows.Add(TR2);
placeHolder.Controls.Add(T); //T is a Table and the placeholder is fed the table.

The problem is that I was attempting the DataBind before I had attached the GridView to any control. Apparently, a dynamic GridView must be a control somewhere on the page prior to data binding.

Wow.

Microsoft is so good at documenting things like this.

answered Sep 26, 2020 at 16:44

John Tamburo

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