Matt Berseth

If you have worked with the ASP.NET 2.0 GridView control, I am sure you were more than a little surprised when you realized there is no decent way to display the Header or Footer rows of a GridView that is bound to an empty DataSource.  I know I was.  It seems like a bug to me and I am surprised it made it through usability testing.  Anyway, there are basically 2 ways to work around this problem:

1. Make your DataSource's return a special empty row so the grid has something to bind to (see example of this here)
2. Subclass GridView and add this functionality yourself

I chose to go with option 2 because because we had already subclassed the GridView for other reasons.  I cheated a little bit and started with the code snippet on the following page.  The GridView control is very complicated and I am not going to claim I understand it entirely, but from what I could tell this starting code segment contains the following bugs:

• It doesn't work when you have AutoGenerateColumns set to true
• It doesn't respect the EmptyDataTemplate (it only accounts for the EmptyDataText)
• It doesn't render the Footer row

So I fixed these bugs and figured I would pass on the resulting code.

You can view a live demo of this in action here, and below is a screen shot of a page using this feature along with all of the code.  Enjoy!

Screen Shot:

Markup:

<mb:GridView 
    runat="server" DataSourceID="sqldsCustomers" 
    ShowHeader="true" ShowHeaderWhenEmpty="true" 
    EmptyDataText="No Customers were found." Width="95%" 
/>

Code:

/// <summary>
/// 
/// </summary>
/// <param name="dataSource"></param>
/// <param name="dataBinding"></param>
/// <returns></returns>
protected override int CreateChildControls(System.Collections.IEnumerable dataSource, bool dataBinding)
{
    int rows = base.CreateChildControls(dataSource, dataBinding);
    
    //  no data rows created, create empty table if enabled
    if (rows == 0 && (this.ShowFooterWhenEmpty || this.ShowHeaderWhenEmpty))
    {
        //  create the table
        Table table = this.CreateChildTable();

        DataControlField[] fields;
        if (this.AutoGenerateColumns)
        {
            PagedDataSource source = new PagedDataSource();
            source.DataSource = dataSource;

            System.Collections.ICollection autoGeneratedColumns = this.CreateColumns(source, true);
            fields = new DataControlField[autoGeneratedColumns.Count];
            autoGeneratedColumns.CopyTo(fields, 0);
        }
        else
        {
            fields = new DataControlField[this.Columns.Count];
            this.Columns.CopyTo(fields, 0);
        }

        if (this.ShowHeaderWhenEmpty)
        {
            //  create a new header row
            GridViewRow headerRow = base.CreateRow(-1, -1, DataControlRowType.Header, DataControlRowState.Normal);
            this.InitializeRow(headerRow, fields);

            //  add the header row to the table
            table.Rows.Add(headerRow);
        }

        //  create the empty row
        GridViewRow emptyRow = new GridViewRow(-1, -1, DataControlRowType.EmptyDataRow, DataControlRowState.Normal);
        TableCell cell = new TableCell();
        cell.ColumnSpan = fields.Length;
        cell.Width = Unit.Percentage(100);

        //  respect the precedence order if both EmptyDataTemplate
        //  and EmptyDataText are both supplied ...
        if (this.EmptyDataTemplate != null)
        {
            this.EmptyDataTemplate.InstantiateIn(cell);
        }
        else if (!string.IsNullOrEmpty(this.EmptyDataText))
        {
            cell.Controls.Add(new LiteralControl(EmptyDataText));
        }

        emptyRow.Cells.Add(cell);
        table.Rows.Add(emptyRow);

        if (this.ShowFooterWhenEmpty)
        {
            //  create footer row
            GridViewRow footerRow = base.CreateRow(-1, -1, DataControlRowType.Footer, DataControlRowState.Normal);
            this.InitializeRow(footerRow, fields);

            //  add the footer to the table
            table.Rows.Add(footerRow);
        }

        this.Controls.Clear();
        this.Controls.Add(table);
    }

    return rows;
}

[Category("Behavior")]
[Themeable(true)]
[Bindable(BindableSupport.No)]
public bool ShowHeaderWhenEmpty
{
    get
    {
        if (this.ViewState["ShowHeaderWhenEmpty"] == null)
        {
            this.ViewState["ShowHeaderWhenEmpty"] = false;
        }

        return (bool)this.ViewState["ShowHeaderWhenEmpty"];
    }
    set
    {
        this.ViewState["ShowHeaderWhenEmpty"] = value;
    }
}

[Category("Behavior")]
[Themeable(true)]
[Bindable(BindableSupport.No)]
public bool ShowFooterWhenEmpty
{
    get
    {
        if (this.ViewState["ShowFooterWhenEmpty"] == null)
        {
            this.ViewState["ShowFooterWhenEmpty"] = false;
        }

        return (bool)this.ViewState["ShowFooterWhenEmpty"];
    }
    set
    {
        this.ViewState["ShowFooterWhenEmpty"] = value;
    }
}