How to Drag Columns Between FlexGrid Controls

C1Flexgrid for WinForms provides OLE Drag/Drop functionality using its DragMode and DropMode properties initiated by dragging of column headers from one grid to another. The OLE Drag and Drop mechanism provides several events which the application traps to implement drag and drop operations from the source to the target. This article explains an approach to move columns between two C1FlexGrid controls.

Enable Drag & Drop

First of all populate the two C1FlexGrid and set their DragMode and DropMode properties to Manual as shown below.

// both are OLE drag sources  
_flexLeft.DragMode = DragModeEnum.Manual;  
_flexRight.DragMode = DragModeEnum.Manual;  

// both are OLE drop targets  
_flexLeft.DropMode = DropModeEnum.Manual;  
_flexRight.DropMode = DropModeEnum.Manual;

Handle Drag & Drop of Columns

To implement the drag/drop operations, you need to handle three events of C1FlexGrid controls.

1. BeforeMouseDown - To initiate DragDrop operation and check if mouse click is done on Column Header

2. DragOver - Handle dragging effects

3. DragDrop - Move Column from Source grid to Target grid

While moving the column from Source to the Target, you will need to verify that the Target object is a C1FlexGrid control.

private void \_flex\_BeforeMouseDown(object sender, C1.Win.C1FlexGrid.BeforeMouseDownEventArgs e)  
{  
       // start dragging when the user clicks the column headers  
       C1FlexGrid flex = sender as C1FlexGrid;  
       HitTestInfo hti = flex.HitTest(e.X, e.Y);  
       if (hti.Type == HitTestTypeEnum.ColumnHeader)  
       {  
             // select the col  
             int indexCol = hti.Column;  
             flex.Select(0, indexCol, flex.Rows.Count - 1, indexCol, false);  

             // save info for target  
             _src = flex;  

             // do drag drop  
             DragDropEffects dd = flex.DoDragDrop(flex.Clip, DragDropEffects.Move);  

             // if it worked, delete column from source (it's a move)  
             if (dd == DragDropEffects.Move)  
                flex.Cols.Remove(indexCol);  

             // done, reset info  
             _src = null;  
        }  
}  

private void \_flex\_DragOver(object sender, System.Windows.Forms.DragEventArgs e)  
{  
     // check whether we can drop here:  
     // we must have a source object, and it should be the  
     // other C1FlexGrid control.  
     if (\_src != null && !\_src.Equals(sender))  
     {  
         // check that we have the type of data we want  
         if (e.Data.GetDataPresent(typeof(string)))  
            e.Effect = DragDropEffects.Move;  
     }  
}  

private void \_flex\_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)  
{  
     C1FlexGrid flex = sender as C1FlexGrid;  
     Point pt = flex.PointToClient(new Point(e.X, e.Y));  
     HitTestInfo hti = flex.HitTest(pt.X, pt.Y);  
     int indexCol = hti.Column;  
     if (indexCol < 0) indexCol = flex.Cols.Count; // append  
        if (indexCol < 1) indexCol = 1;               // after fixed column  

     // insert a new col at the drop position  
     flex.Cols.Insert(indexCol);  

     // copy data from source row  
     flex.Select(0, indexCol, flex.Rows.Count - 1, indexCol, false);// flex.Cols.Count-1, false);  
     flex.Clip = (string)e.Data.GetData(typeof(string));  
}