Question

ASP.Net:

<asp:GridView id ="sampleGridView" AutoGenerateEditButton ="True" OnRowEditing ="sampleGridView_RowEditing" OnRowCancelingEdit ="sampleGridView_RowCancelingEdit" OnRowUpdating ="sampleGridView_RowUpdating" runat ="server"></asp:GridView>

Code Behind:

public partial class _Default : System.Web.UI.Page
{
    private DataTable dt = new DataTable("SampleTable");

    protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack){
           PopulateGridView();     
        }
    }
    private void PopulateGridView()
    {
        dt.Columns.Add("Name", typeof(string));
        dt.Columns.Add("Desgnation", typeof(string));
        dt.Columns.Add("City", typeof(string));
        for (int i = 0; i < src.GetLength(0); i++)
        {
            dt.Rows.Add(src[i, 0], src[i, 1], src[i, 2]);
        }
        sampleGridView.DataSource = dt;
        sampleGridView.DataBind();

    }
    protected void sampleGridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        GridViewRow row = sampleGridView.Rows[e.RowIndex];
        //Response.Write(src[1,0]+" "+ dt.Rows[0][0]);
        dt.Rows[row.DataItemIndex]["Name"] = ((TextBox)(row.Cells[1].Controls[0])).Text;
        dt.Rows[row.DataItemIndex]["Desgnation"] = ((TextBox)(row.Cells[1].Controls[0])).Text;
        dt.Rows[row.DataItemIndex]["City"] = ((TextBox)(row.Cells[3].Controls[0])).Text;
    }
}

System.IndexOutOfRangeException: There is no row at position {Row Number} say 2. is the error in sampleGridView_RowUpdating at the line

dt.Rows[row.DataItemIndex]["Name"] = ((TextBox)(row.Cells[1].Controls[0])).Text;

I tried following code commenting out the above error generating code

Response.Write(dt.Columns.Count+" "+dt.TableName);

Output is :
0 SampleTable

Why datatable values cant be accessed ?

Answer 1

When you manually populate a page’s members you need to do on every request if you need it to persist between postbacks. This is often done using session state.

For example

    protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack){
           PopulateGridView();     
        }
        else
        {
           dt = (DataTable)Session["YourDatatable"]; //retrieve it from session
           sampleGridView.DataSource = dt;
           sampleGridView.DataBind();
        }
    }
    private void PopulateGridView()
    {
        dt.Columns.Add("Name", typeof(string));
        dt.Columns.Add("Desgnation", typeof(string));
        dt.Columns.Add("City", typeof(string));
        for (int i = 0; i < src.GetLength(0); i++)
        {
            dt.Rows.Add(src[i, 0], src[i, 1], src[i, 2]);
        }
        sampleGridView.DataSource = dt;
        sampleGridView.DataBind();

        Session["YourDatatable"] = dt; //Store it for later

    }