Worksheet protected range doesn't allow paste operation

hi,
I have used the code snippet below to edit a specific range in the protected spreadsheetcontrol

C#
using DevExpress.Spreadsheet;  
// ...  
workbook.BeginUpdate();  
Worksheet worksheet = workbook.Worksheets[0];  
// Give specific user permission to edit a range in a protected worksheet  
ProtectedRange protectedRange = worksheet.ProtectedRanges.Add("My Range", worksheet["C3:E8"]);  
EditRangePermission permission = new EditRangePermission();  
permission.UserName = Environment.UserName;  
permission.DomainName = Environment.UserDomainName;  
permission.Deny = false;  
protectedRange.SecurityDescriptor = protectedRange.CreateSecurityDescriptor(new EditRangePermission[] { permission });  
//protectedRange.SetPassword("123");  

// Protect a worksheet  
if (!worksheet.IsProtected)  
    worksheet.Protect("password", WorksheetProtectionPermissions.Default);  

workbook.EndUpdate();  

The worksheet["C3:E8"] range  can be edited,but pasting dosen't work