i got this soluiton from one of my projects it will help u just need to change the field name and column value
HTML CODE
<Columns>
<telerik:GridTemplateColumn UniqueName="Checked">
<ItemTemplate>
<asp:CheckBox ID="chkPermission" runat="server" AutoPostBack="true" OnCheckedChanged="chkPermission_Checked" />
</ItemTemplate>
<HeaderTemplate>
<asp:CheckBox ID="headerChkbox" runat="server" OnCheckedChanged="ToggleSelectedState"
AutoPostBack="true" />
</HeaderTemplate>
</telerik:GridTemplateColumn>
<telerik:GridTemplateColumn UniqueName="PermissionID" Visible="false">
<ItemTemplate>
<asp:HiddenField ID="hfPermissionID" runat="server" Value='<%#Eval("PermissionID") %>' />
</ItemTemplate>
</telerik:GridTemplateColumn>
<telerik:GridBoundColumn DataField="PermissionTypeName" HeaderText="PermissionTypeName"
SortExpression="PermissionTypeName" UniqueName="PermissionTypeName">
</telerik:GridBoundColumn>
</Columns>
AND IN CODE BEHIND U CAN USE FOLLOWING FUNCTION JUST TO GET THAT SELECTED ID's AND LOOP THROUGH EACH OF THEM AND DO WHATEVER U WANT TO DO
Protected Sub ToggleSelectedState(ByVal sender As Object, ByVal e As EventArgs)
Dim headerCheckBox As CheckBox = TryCast(sender, CheckBox)
For Each dataItem As GridDataItem In rgPermission.MasterTableView.Items
TryCast(dataItem.FindControl("chkPermission"), CheckBox).Checked = headerCheckBox.Checked
dataItem.Selected = headerCheckBox.Checked
Next
End Sub
Public Sub chkPermission_Checked(ByVal sender As Object, ByVal e As EventArgs)
Dim chkEmail As CheckBox = TryCast(sender, CheckBox)
For Each dataItem As GridDataItem In rgPermission.MasterTableView.Items
If TryCast(dataItem.FindControl("chkPermission"), CheckBox).Checked Then
dataItem.Selected = True
Else
dataItem.Selected = False
End If
Next
End Sub
Protected Sub btnAddnPermission_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAddnPermission.Click
For Each dataItem As GridDataItem In rgPermission.MasterTableView.Items
If TryCast(dataItem.FindControl("chkPermission"), CheckBox).Checked Then
hfPermissionID.Value += (TryCast(dataItem.FindControl("hfPermissionID"), HiddenField).Value) + "|"
End If
Next
If hfPermissionID.Value <> "" Then
Dim test As String = hfPermissionID.Value
Dim myStringArr() As String = Split(test, "|")
Dim userID As Integer = CInt(ddlADUser.SelectedValue)
If myStringArr IsNot Nothing Then
Dim i As Integer = 0
For Each s As String In myStringArr
Dim IDs As String = myStringArr(i).ToString
If IDs <> "" Then
Try
boolVal = df.InsertPermissionByUserID(userID, CInt(IDs))
Catch ex As Exception
ErrorMessage(ex.InnerException.Message)
End Try
End If
i += 1
Next
End If
End Sub
NOTE IN MY FOR EACH LOOP ID's IS THE ID OF THE VALUE I HAVE SELECTED FROM RADGRID
AND TO STORE THAT VALUE IM USING HIDDEN FIELD IN RADGRID ITEM TEMPLATE.....HOPE IT WILL HELP YOU....