Manually update some items in FormView using EntityDataSource (ASP.NET)

Question

Hi! What is the best way to manually update some items in a formview using Entity Framework?

For example, I would like the user to select from a Checkbox list a few categories which the user will check the relavant ones. I would like to store those checked items as a comma seperated text in the database.

If I am using SQL DataSource, I could do something like this:

protected void FormView1_ItemUpdating(object sender, FormViewUpdateEventArgs e)  
{  
 CheckBoxList cboxlist = FormView1.FindControl("CheckBoxList1") as CheckBoxList;  
 if (cboxlist != null)  
 {  
     System.Text.StringBuilder sb = new System.Text.StringBuilder();  
     foreach (ListItem item in cboxlist.Items)  
     {  
         if (item.Selected)  
         {  
             sb.AppendFormat("{0},", item.Value);  
         }  
     }  
     if (sb.Length > 0)  
     {  
         SqlDataSource1.UpdateParameters["category_csv"].DefaultValue = sb.ToString().TrimEnd(',');  
     }  
 }  

}  

However, there is no UpdateCommand in the EntityDataSource anymore, thus UpdatePArameter would not be of any use anymore..

What is the best way to do so?