gridview merge column headers

Question

I have a gridview and I want to merge the headers of column (n) and (n+1) into one so that the output will use colspan to show a single header for columns n and n+1. I\'ve s

Answer 1

i created this solution example

To run in your local system will will need to create 2 files ( one for the control and one aspx) you can either do it one project or 2 projects.

1. GridViewPlus ==> Control class
2. GridViewPlusCustomHeaderRows ==> a collection to hold custom header class
3. CustomHeaderEventArgs ==> Event Args when custom header row is created

4. aspx file ==> Test program

   public class GridViewPlus : GridView
   {
   
       public event EventHandler CustomHeaderTableCellCreated;
   
       private GridViewPlusCustomHeaderRows _rows;
   
       public GridViewPlus() : base ()
       {
           _rows = new GridViewPlusCustomHeaderRows();
       }
   
       /// 
   
       /// Allow Custom Headers
       /// 
       public bool ShowCustomHeader { get; set; }
   
   
       [PersistenceMode(PersistenceMode.InnerDefaultProperty)]
       [MergableProperty(false)]
       public GridViewPlusCustomHeaderRows CustomHeaderRows
       {
           get {return  _rows; }
   
       }
   
       protected virtual void OnCustomHeaderTableCellCreated(CustomHeaderEventArgs e)
       {
           EventHandler handler = CustomHeaderTableCellCreated;
   
           // Event will be null if there are no subscribers
           if (handler != null)
           {
               // Use the () operator to raise the event.
               handler(this, e);
           }
   
       }
   
       protected override void OnRowCreated(GridViewRowEventArgs e)
       {
           if (ShowCustomHeader && e.Row.RowType == DataControlRowType.Header) return;
           base.OnRowCreated(e);
       }
   
   
       protected override void PrepareControlHierarchy()
       {
           //Do not show the Gridview header if show custom header is ON
           if (ShowCustomHeader) this.ShowHeader = false;
   
   
           base.PrepareControlHierarchy();
           //Safety Check
           if (this.Controls.Count == 0)
               return;
           bool controlStyleCreated = this.ControlStyleCreated;
           Table table = (Table)this.Controls[0];
   
           int j = 0;
           if (CustomHeaderRows ==null )return ;
   
           foreach (TableRow tr in CustomHeaderRows)
           {
               OnCustomHeaderTableCellCreated(new CustomHeaderEventArgs(tr,j));
               table.Rows.AddAt(j, tr);
               tr.ApplyStyle(this.HeaderStyle);
               j++;
           }
   
   
       }
   }
   
   public class GridViewPlusCustomHeaderRows : System.Collections.CollectionBase
   {
       public GridViewPlusCustomHeaderRows()
       {
       }
   
       public void Add(TableRow aGridViewCustomRow)
       {
           List.Add(aGridViewCustomRow);
       }
   
       public void Remove(int index)
       {
           // Check to see if there is a widget at the supplied index.
           if (index > Count - 1 || index < 0)
           // If no widget exists, a messagebox is shown and the operation 
           // is cancelled.
           {
               throw (new Exception("Index not valid"));
           }
           else
           {
               List.RemoveAt(index);
           }
       }
   
       public TableRow Item(int Index)
       {
           // The appropriate item is retrieved from the List object and
           // explicitly cast to the Widget type, then returned to the 
           // caller.
           return (TableRow)List[Index];
       }
   
   }
   
   
   public class CustomHeaderEventArgs : EventArgs
   {
       public CustomHeaderEventArgs(TableRow tr ,int RowNumber  )
       {
           tRow = tr;
           _rownumber = RowNumber;
       }
       private TableRow tRow;
       private int _rownumber = 0;
   
   
       public int RowNumber { get { return _rownumber; } }
   
       public TableRow HeaderRow
       {
           get { return tRow; }
           set { tRow = value; }
       }
   
   
   }
   
   
   public partial class _Default : System.Web.UI.Page
   {
       protected void Page_Load(object sender, EventArgs e)
       {
           Example1();
           GridViewExtension1.CustomHeaderTableCellCreated += new EventHandler(GridViewExtension1_CustomHeaderTableCellCreated);
       }
   
       void GridViewExtension1_CustomHeaderTableCellCreated(object sender, CustomHeaderEventArgs e)
       {
           TableRow tc = (TableRow)e.HeaderRow;
   
           tc.BackColor = System.Drawing.Color.AliceBlue;
       }
   
       private void Example1()
       {
           System.Data.DataTable dtSample = new DataTable();
           DataColumn dc1 = new DataColumn("Column1",typeof(string));
           DataColumn dc2 = new DataColumn("Column2",typeof(string));
           DataColumn dc3 = new DataColumn("Column3",typeof(string));
           DataColumn dc4 = new DataColumn("Column4",typeof(string));
          // DataColumn dc5 = new DataColumn("Column5",typeof(string));
           dtSample.Columns.Add(dc1);
           dtSample.Columns.Add(dc2);
           dtSample.Columns.Add(dc3);
           dtSample.Columns.Add(dc4);
          // dtSample.Columns.Add(dc5);
           dtSample.AcceptChanges();
   
           for (int i = 0; i < 25; i++)
           {
               DataRow dr = dtSample.NewRow();
   
               for (int j = 0; j < dtSample.Columns.Count; j++)
               {
                   dr[j] = j;
               }
               dtSample.Rows.Add(dr);
           }
           dtSample.AcceptChanges();
           //GridViewExtension1.ShowHeader = false;
           GridViewExtension1.ShowCustomHeader = true;
   
           /*
            *=======================================================================
            *  |Row 1 Cell 1   |   Row 1 Col 2 (Span=2)        | Row 1 Col 3   |
            *  |               |                               |               |
            *=======================================================================             
            *  |Row 2 Cell 1   |               |               |               |
            *  |               |   Row 2 Col 2 | Row 2 Col 3   |Row 2 Col 4    |
            *=======================================================================
            * 
            * 
            * 
            * 
            * */
   
           // SO we have to make 2 header row as shown above
   
           TableRow TR1 = new TableRow();
           TableCell tcR1C1 = new TableCell();
           tcR1C1.Text = "Row 1 Cell 1";
           tcR1C1.ColumnSpan = 1;
           TR1.Cells.Add(tcR1C1);       
   
           TableCell tcR1C2 = new TableCell();
           tcR1C2.Text = "Row 1 Cell 2";
           tcR1C2.ColumnSpan = 2;
           TR1.Cells.Add(tcR1C2);  
   
           TableCell tcR1C3 = new TableCell();
           tcR1C3.Text = "Row 1 Cell 3";
           tcR1C3.ColumnSpan = 1;
           TR1.Cells.Add(tcR1C3);
   
   
           GridViewExtension1.CustomHeaderRows.Add(TR1);
   
           TableRow TR2 = new TableRow();
           TableCell tcR2C1 = new TableCell();
           tcR2C1.Text = "Row 2 Cell 1";
           tcR2C1.ColumnSpan = 1;
           TR2.Cells.Add(tcR2C1);
   
           TableCell tcR2C2 = new TableCell();
           tcR2C2.Text = "Row 2 Cell 2";
           tcR2C2.ColumnSpan = 1;
           TR2.Cells.Add(tcR2C2);
   
           TableCell tcR2C3 = new TableCell();
           tcR2C3.Text = "Row 2 Cell 3";
           tcR2C3.ColumnSpan = 1;
           TR2.Cells.Add(tcR2C3);
   
           TableCell tcR2C4 = new TableCell();
           tcR2C4.Text = "Row 2 Cell 4";
           tcR2C4.ColumnSpan = 1;
           TR2.Cells.Add(tcR2C4);
   
           GridViewExtension1.CustomHeaderRows.Add(TR2);
   
   
           GridViewExtension1.DataSource = dtSample;
           GridViewExtension1.DataBind();
   
       }
   }