Deleting Records

There are generally two ways to perform a delete operation inside RadTreeList:

• Through the automatic operations provided by the control.

• Manually, by wiring the ItemCommand or DeleteCommand event of the control.

In both cases, the most straightforward way to trigger the delete is to use a TreeListButtonColumn with a CommandName property set to "Delete".

Deleting records using automatic operations

You can take advantage of the automatic data source operations of RadTreeList by setting up a data source control to allow deletes and binding the treelist to it. Additionally, if you allow cascade deletes for your database, you can set the AllowRecursiveDelete property to "true" which will take care of deleting all child items (if any) of the currently deleted item.

Deleting records manually

The manual delete operations in RadTreeList consist of two main parts:

1. Accessing the data key value of the item to be deleted.

2. Using it to find the record inside the treelist's data source and deleting it.

Once the user clicks the delete button inside the treelist, you can handle the DeleteCommand event and perform these steps there. The code snippet below demonstrated a possible approach:

<telerik:RadTreeList RenderMode="Lightweight" ID="RadTreeList1" runat="server" DataKeyNames="ID" ParentDataKeyNames="ParentID"
    AutoGenerateColumns="false" OnNeedDataSource="RadTreeList1_NeedDataSource" OnDeleteCommand="RadTreeList1_DeleteCommand">
    <Columns>
        <telerik:TreeListBoundColumn DataField="ID" UniqueName="ID" HeaderText="ID">
        </telerik:TreeListBoundColumn>
        <telerik:TreeListBoundColumn DataField="Name" UniqueName="Name" HeaderText="Name">
        </telerik:TreeListBoundColumn>
        <telerik:TreeListBoundColumn DataField="ParentID" UniqueName="ParentID" HeaderText="ParentID">
        </telerik:TreeListBoundColumn>
        <telerik:TreeListButtonColumn HeaderText="Delete" CommandName="Delete" Text="Delete" />
    </Columns>
</telerik:RadTreeList>

protected void RadTreeList1_NeedDataSource(object sender, TreeListNeedDataSourceEventArgs e)
{
    RadTreeList1.DataSource = GetDataTable();
}

protected void RadTreeList1_DeleteCommand(object sender, TreeListCommandEventArgs e)
{
    //accessing the datakey value through the server API of the TreeListDataItem
    string dataKeyValue = (e.Item as TreeListDataItem).GetDataKeyValue("ID").ToString();
    //the actual deletion logic depends on the kind of data source that you use, your only task is to remove the item from the data source. The RadTreeList control will implicitly rebind itself afterwards.
    String ConnString = ConfigurationManager.ConnectionStrings["TelerikConnectionString"].ConnectionString;
    SqlConnection conn = new SqlConnection(ConnString);
    SqlCommand deleteCommand = new SqlCommand("DELETE FROM SelfReferencing WHERE ID='" + dataKeyValue + "'", conn);
    conn.Open();
    try
    {
        deleteCommand.ExecuteNonQuery();
    }
    finally
    {
        conn.Close();
    }
}

public DataTable GetDataTable()
{
    String ConnString = ConfigurationManager.ConnectionStrings["TelerikConnectionString"].ConnectionString;
    SqlConnection conn = new SqlConnection(ConnString);
    SqlDataAdapter adapter = new SqlDataAdapter();
    adapter.SelectCommand = new SqlCommand("SELECT ID, Name, ParentID FROM SelfReferencing", conn);

    DataTable myDataTable = new DataTable();
    conn.Open();
    try
    {
        adapter.Fill(myDataTable);
    }
    finally
    {
        conn.Close();
    }
    return myDataTable;
}

Protected Sub RadTreeList1_NeedDataSource(ByVal sender As Object, ByVal e As TreeListNeedDataSourceEventArgs)
    RadTreeList1.DataSource = GetDataTable()
End Sub

Protected Sub RadTreeList1_DeleteCommand(ByVal sender As Object, ByVal e As TreeListCommandEventArgs)
    'accessing the data key value through the server API of the TreeListDataItem
    Dim dataKeyValue As String = TryCast(e.Item, TreeListDataItem).GetDataKeyValue("ID").ToString()
    'the actual deletion logic depends on the kind of data source that you use, your only task is to remove the item from the data source. The RadTreeList control will implicitly rebind itself afterwards.
    Dim ConnString As [String] = ConfigurationManager.ConnectionStrings("TelerikConnectionString").ConnectionString
    Dim conn As New SqlConnection(ConnString)
    Dim deleteCommand As New SqlCommand("DELETE FROM SelfReferencing WHERE ID='" + dataKeyValue + "'", conn)
    conn.Open()
    Try
        deleteCommand.ExecuteNonQuery()
    Finally
        conn.Close()
    End Try
End Sub

Public Function GetDataTable() As DataTable
    Dim ConnString As [String] = ConfigurationManager.ConnectionStrings("TelerikConnectionString").ConnectionString
    Dim conn As New SqlConnection(ConnString)
    Dim adapter As New SqlDataAdapter()
    adapter.SelectCommand = New SqlCommand("SELECT ID, Name, ParentID FROM SelfReferencing", conn)

    Dim myDataTable As New DataTable()
    conn.Open()
    Try
        adapter.Fill(myDataTable)
    Finally
        conn.Close()
    End Try
    Return myDataTable
End Function

Please note that with this approach you might need to take care of deleting the child items of the deleted item as well.