Binding GridView to DataTable does not show data in the GridView, the GridView is empty

Question

I am working in ASP.Net with C# as code behind. The editor is Visual Studio 2012. I created a GridView with 5 columns: the first one contains checkboxes, the next 3 have text boxes and the last one is a buttonfield, as follows (I have made AutoGenerateColumns as false because, otherwise DataBind adds more columns":

<asp:GridView ID="gvCDS" runat="server" AutoGenerateColumns="False"     OnRowDeleting="gvCDS_RowDeleting">
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:CheckBox ID="cbSelectedCDS" runat="server" Enabled="true"/>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Module Code">
            <ItemTemplate>
                <asp:TextBox ID="tbxInputCDSModuleCode" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Module Name">
            <ItemTemplate>
                <asp:TextBox ID="tbxInputCDSModuleName" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Credit Units">
            <ItemTemplate>
                <asp:TextBox ID="tbxInputCDSCreditUnits" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:ButtonField Text="Clear Module" />
    </Columns>

I need to show the GridView on selecting an item from a dropdown. The GridView always needs to have 8 rows. I have written the following code to show the GridView:

DataTable dt = ViewState["dt"] as DataTable;
if (dt == null)
{
    dt = new DataTable();
    dt.Columns.Add("", typeof(Boolean));
    dt.Columns.Add("Module Code", typeof(String));
    dt.Columns.Add("Module Name", typeof(String));
    dt.Columns.Add("Credit Units", typeof(String));

    for (int i = 0; i < 8; i++)
    {
        dt.Rows.Add(dt.NewRow());
    }
}
gvCDS.DataSource = dt;
gvCDS.DataBind();
ViewState["dt"] = dt;
gvCDS.Visible = true;

The user makes some inputs in the GridView and then clicks a button. In the button's click event procedure, I need to delete the checked rows from the GridView and add rows so that total number of rows remains as 8. If I simply call .DeleteRow method, the row is not getting deleted. I still see the GridView as earlier in the browser. So I first copy the content of GridView into DataTable as follows:

DataTable dt = ViewState["dt"] as DataTable;
int rowCounter = 0;
foreach (GridViewRow row in gvCDS.Rows)
{
    DataRow dr = dt.Rows[rowCounter];
    dr[0] = ((CheckBox)row.FindControl("cbSelectedCDS")).Checked;
    dr[1] = ((TextBox)row.FindControl("tbxInputCDSModuleCode")).Text;
    dr[2] = ((TextBox)row.FindControl("tbxInputCDSModuleName")).Text;
    dr[3] = ((TextBox)row.FindControl("tbxInputCDSCreditUnits")).Text;
    rowCounter++;
}

After that, instead of deleting rows from the GridView, I delete from the DataTable as follows:

rowCounter = 0;
int rowsDeleted = 0;
foreach (GridViewRow row in gvCDS.Rows)
{
    if (((CheckBox)row.FindControl("cbSelectedCDS")).Checked)
    {
        dt.Rows.RemoveAt(rowCounter);
        rowsDeleted++;
    }
    else
    {
        rowCounter++;
    }  
}

rowsDeleted now contains the number of rows that were deleted. I add that many rows in the DataTable so that the total number of rows remains as 8.
for (i = 0; i < rowsDeleted; i++)
{
    dt.Rows.Add(dt.NewRow());
}

After that I bind GridView to DataTable as follows:

ViewState["dt"] = dt;
gvCDS.DataSource = dt;
gvCDS.DataBind();

The GridView still has 8 rows. That is correct. But the problem is that the entire GridView has become empty. When testing, I filled some of the rows and checked only one of them. So, the content of the unchecked rows should be there. But the entire GridView is empty. I do not know why. Not only that, I even tested by keeping all rows unchecked, which means no row will be deleted. Still, the GridView becomes all empty. How do I solve this problem? Thank you.

I noticed in the code you are using to display the grid that you are explicitly setting the grid to visible: gvCDS.Visible = true;. Is there any reason why you are not doing this on the rebind? — Karl Anderson
The grid needs to be shown only if the user selects one particular item from the drop down. So when he selects that item, I set visible to true, else I set visible to false. I have pasted only the portion of the code in which the user selects that particular item. In rebind, the grid is already visible. — Avinash

afzalulh afzalulh · Accepted Answer · 2013-11-30T03:09:47

Issue is your Text Boxes inside GridView are not bound to any field. Bind their Texts to the fields like Text='<%# Eval("Field")%>'.

Change your GridView markup to this:

<asp:GridView ID="gvCDS" runat="server" AutoGenerateColumns="False"     OnRowDeleting="gvCDS_RowDeleting">
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:CheckBox ID="cbSelectedCDS" runat="server" Enabled="true" />
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Module Code">
            <ItemTemplate>
                <asp:TextBox ID="tbxInputCDSModuleCode" Text='<%# Eval("Module Code")%>' runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Module Name">
            <ItemTemplate>
                <asp:TextBox ID="tbxInputCDSModuleName" Text='<%# Eval("Module Name")%>' runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Credit Units">
            <ItemTemplate>
                <asp:TextBox ID="tbxInputCDSCreditUnits"  Text='<%# Eval("Credit Units")%>' runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:ButtonField Text="Clear Module"/>
    </Columns>
</asp:GridView>

Binding GridView to DataTable does not show data in the GridView, the GridView is empty

1 Answers