Question

Why can’t i change the value in a specific row in the rowdatabound event of my gridview? the code is entering where the value is set to Test but still shows old value?

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
    DataKeyNames="au_id" DataSourceID="SqlDataSource1" 
    ondatabinding="GridView1_DataBinding" onrowdatabound="GridView1_RowDataBound">
    <Columns>
        <asp:BoundField DataField="au_id" HeaderText="au_id" ReadOnly="True" 
            SortExpression="au_id" />
        <asp:BoundField DataField="au_lname" HeaderText="au_lname" 
            SortExpression="au_lname" />
        <asp:BoundField DataField="au_fname" HeaderText="au_fname" 
            SortExpression="au_fname" />
    </Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" 
    ConnectionString="<%$ ConnectionStrings:pubsConnectionString %>" 
    SelectCommand="SELECT [au_id], [au_lname], [au_fname] FROM [authors]">
</asp:SqlDataSource>


protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        var row = ((DataRowView)e.Row.DataItem).Row;

        var customerName = row.Field<String>("au_lname");
        if (customerName == "Carson")
        {
            customerName = "Test";
        }
    } 
}

Answer 1

Because you cannot change the underlying DataSource in RowDataBound(too late). You need to apply your changes to the TemplateFields controls or to the CellCollection of the row(in case of BoundFields or AutogenerateColumns=true):

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        DataRow row = ((DataRowView)e.Row.DataItem).Row;
        var customerName = row.Field<String>("au_lname");
        if (customerName == "Carson")
        {
            e.Row.Cells[1].Text = "Test";
        }else
        {
            e.Row.Cells[1].Text = customerName;
        }
    }
}