In Dynamic Data, how to merge cells with equal values in the generated GridView

Question

I am using ASP.NET Dynamic Data to generate a web site for several data tables, and so far so good.

But there is a request from the customer that they want to merge cells with equal values in the GridView.

I have got a solution CodeProject and it works well in a normal ASP.NET page.

However, it simply merges all the rows into one row in a Dynamic Data generated GridView. I traced the source code and find out that in the GridView_PreRender method, the row.Cells[cellIndex].Text is always empty!

SO, I can not judge if two cells are the same. Is anyone have encountered such problem before?

Answer 1

Based on my research in order to get values of GridView's cells on PreRender event in ASP.NET Dynamic Data you need to do the following things:

1. Find the FieldTemplate in the cell's controls collection
2. Cast FieldTemplate to FieldTemplateUserControl to gain access to it properties

I have just simulated your problem based on my project.

List.aspx.cs:

protected void gvOffices_PreRender(object sender, EventArgs e)
{
    for (int rowIndex = gvOffices.Rows.Count - 2; rowIndex >= 0; rowIndex--)
    {
        GridViewRow row = gvOffices.Rows[rowIndex];
        GridViewRow previousRow = gvOffices.Rows[rowIndex + 1];

        if (row.RowType == DataControlRowType.DataRow)
        {
            for (int i = 0; i < row.Cells.Count; i++)
            {
                string dataField = ((DynamicField)((DataControlFieldCell)row.Cells[i]).ContainingField).DataField;
                Control dataControl = ((FieldTemplateUserControl)((DynamicControl)row.Cells[i].FindDynamicControlRecursive(dataField)).FieldTemplate).DataControl;
                string cellText = ((Literal)dataControl).Text; // for text fields

                string dataFieldPrev = ((DynamicField)((DataControlFieldCell)previousRow.Cells[i]).ContainingField).DataField;
                Control dataControlPrev = ((FieldTemplateUserControl)((DynamicControl)previousRow.Cells[i].FindDynamicControlRecursive(dataField)).FieldTemplate).DataControl;
                string cellTextPrev = ((Literal)dataControl).Text; // for text fields

                Response.Write(cellText);
                Response.Write(cellTextPrev);

                //if (cellText == cellTextPrev)
                //{
                //    row.Cells[i].RowSpan = previousRow.Cells[i].RowSpan < 2 ? 2 :
                //                           previousRow.Cells[i].RowSpan + 1;
                //    previousRow.Cells[i].Visible = false;
                //}
            }
        }
    }
}

FindDynamicControlRecursive() you can find at http://csharpbits.notaclue.net/2009/01/dynamic-data-cascading-fieldtemplates.html.

Consider this technique in your project. I hope this will help.

EDIT 1:

Also we need to check if a control inside GridView cell is HyperLink or Literal:

if (dataControl is Literal)
{
    cellText = ((Literal)dataControl).Text;
}
else
{
    if (dataControl is HyperLink)
    {
        cellText = ((HyperLink)dataControl).Text;
    }
}

EDIT 2: (It works fine for me)

Check if a control inside GridView cell is DynamicField:

protected void gvOffices_PreRender(object sender, EventArgs e)
{
    for (int rowIndex = gvOffices.Rows.Count - 2; rowIndex >= 0; rowIndex--)
    {
        GridViewRow row = gvOffices.Rows[rowIndex];
        GridViewRow previousRow = gvOffices.Rows[rowIndex + 1];

        if ((row.RowType == DataControlRowType.DataRow) && (previousRow.RowType == DataControlRowType.DataRow))
        {
            for (int i = 0; i < row.Cells.Count; i++)
            {
                // check for the current row
                if (((DataControlFieldCell)row.Cells[i]).ContainingField is DynamicField)
                {
                    string dataField = ((DynamicField)((DataControlFieldCell)row.Cells[i]).ContainingField).DataField;
                    Control dataControl = ((FieldTemplateUserControl)((DynamicControl)row.Cells[i].FindDynamicControlRecursive(dataField)).FieldTemplate).DataControl;

                    string cellText = string.Empty;
                    if (dataControl is Literal)
                    {
                        cellText = ((Literal)dataControl).Text;
                    }
                    else
                    {
                        if (dataControl is HyperLink)
                        {
                            cellText = ((HyperLink)dataControl).Text;
                        }
                    }

                    // get cells text of the current row
                    Response.Write(cellText);
                }

                // check for the previous row
                if (((DataControlFieldCell)previousRow.Cells[i]).ContainingField is DynamicField)
                {
                    string dataFieldPrev = ((DynamicField)((DataControlFieldCell)previousRow.Cells[i]).ContainingField).DataField;
                    Control dataControlPrev = ((FieldTemplateUserControl)((DynamicControl)previousRow.Cells[i].FindDynamicControlRecursive(dataFieldPrev)).FieldTemplate).DataControl;

                    string cellTextPrev = string.Empty;
                    if (dataControlPrev is Literal)
                    {
                        cellTextPrev = ((Literal)dataControlPrev).Text;
                    }
                    else
                    {
                        if (dataControlPrev is HyperLink)
                        {
                            cellTextPrev = ((HyperLink)dataControlPrev).Text;
                        }
                    }

                    // get cells text of the previous row
                    Response.Write(cellTextPrev);
                }

                // Try to merge cells

                //if (cellText == cellTextPrev)
                //{
                //    row.Cells[i].RowSpan = previousRow.Cells[i].RowSpan < 2 ? 2 :
                //                           previousRow.Cells[i].RowSpan + 1;
                //    previousRow.Cells[i].Visible = false;
                //}
            }
        }
    }
}