Category Archives: csharp

SelectionChangedEvent in RadGridView

If you have used RadGridView with a GridViewComboBoxColumn, you know it does not support SelectionChangedEvent directly. There are many scenarios where you want to handle some validation or perform some action when the user selects an item in a combo box but the absense of SelectionChangedEvent for GridViewComboBoxColumn makes this really hard. Good news is, there is a solution. Here it is, see if it helps.

Let’s say you have a RadGridView defined like this:


<telerik:RadGridView x:Name="myGridView">
 <telerik:RadGridView.Columns>
 <telerik:GridViewComboBoxColumn Header="Page" UniqueName="column1"  />
 </telerik:RadGridView.Columns>
</telerik:RadGridView>

 
In your code behind, preferably in the Loaded event, add this code:


this.AddHandler(RadComboBox.SelectionChangedEvent,
new Telerik.Windows.Controls.SelectionChangedEventHandler(ComboBox_SelectionChanged));

Add an event for Selection changed event. The name of your method and the event above should match.


 void ComboBox_SelectionChanged(object sender, RadRoutedEventArgs args)
 {
RadComboBox comboBox = (RadComboBox)args.OriginalSource;

if (comboBox.SelectedValue == null)
return;

// Get the current cell
GridViewCell cell = myGridView.CurrentCell;

// Handle the situation where a cell is null. It can be when you are adding a new row
if (cell == null)
{
return;
}

GridViewRowItem row = cell.ParentRow;
GridViewColumn col = cell.Column;

// This if block here is to handle only the combo box column desired. You can
// have multiple combobox columns and this event will be triggered for all of them.
// Handle what is required and ignore the rest
if (col.UniqueName != "column1") // Unique name that you specified in the XAML
{
return;
}

// YourDataObject is whatever data object you are using
YourDataObject item = comboBox.DataContext as YourDataObject;

//SelectedItem returns object. Convert it to whatever your binding object type is
object selectedItem = comboBox.SelectedItem;

// Now that you have your selected item, you can do whatever you want.
// In case you want to disable other cells on this row, just use row.Cells property.
}

That’s it. You are all set now.

Some points to note:
1. SelectionChanged event will be triggered for all combo box columns and combo boxes you have. You need to find out if the deisred combo box column is changed.
2. This event is triggered not only after the selection is changed, but also when the user just clicks on the combo box. There is a solution to handle this, but that’s another story altogether.
3. This was tried with VS 2010 and Silverlight 4.

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DataGridViewComboBoxColumn requires multiple clicks to select an item

If you have ever used a DataGridView with a DataGridViewComboBox column, then you would have definitely noticed that you need multiple clicks to select an item in the combo box. This is very annoying because every time you want to select a different item from the combo box, you need at least 2-3 clicks.

Fix

Fortunately, there is a simple fix for this: set the EditMode property of the data grid view to EditOnEnter. So, when the user enters the control, the cell is automatically put in edit mode, so when you actually click on the combo box, you can see the drop down list.
A bug

That being said, there is a bug associated with this. With the EditMode property set to EditOnEnter, when you select a row by clicking on the row header, the entire row is selected, but one cell will be in edit mode. What this means is if you try to delete the row by selecting the row header, you cannot delete the row because the delete key is actually being sent to the cell being edited and not the row.

This page has more details on this bug and also a workaround.

Right click on TreeView: Get the node clicked at

Problem:

There is a TreeView control with n number of nodes. When the user right clicks on the TreeView control, get the node on which the right click was performed.

Background:

In TreeView control, SelectedNode property is set whenever left click occurs. This is not true for right clicks. So, we need to have some workaround for this.

Solution 1:

The most popular solution is to handle the MouseDown event. Check if the click was a right click and then use the TreeView control’s GetNodeAt API to get the node which was clicked at.

private void treeView1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Right)
{
TreeNode selectedNode = treeView1.GetNodeAt(e.X, e.Y);
MessageBox.Show("You clicked on node: " + selectedNode.Text);
}
}


Solution 2:

Handle the NodeMouseClick event. The TreeNodeMouseClickEventArgs has the node which was clicked at.

private void treeView1_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
{
if (e.Button == MouseButtons.Right)
{
MessageBox.Show("You clicked on node: " + e.Node.Text, "Solution 2");
}
}

SelectedNode property of a treeview is set whenever a left click occurs. Why can’t the same be applied for right click? Right click on a treeview is such a common UI event, that users will benefit from it.