AttachAll exception: type arguments for method cannot be inferred from the usage. Try specifying the type arguments explicitly

Question

Scenario: Trying to call the .AttachAll method on a table in my LinqToSql DataContext object.

Here's the relevant simplified snippet:

  public void Update(Customer cust){
    MyDataContext db = new MyDataContext();            
    db.CustomerInvoices.AttachAll(cust.Invoices);  //exception raised here!
    db.Customer.Attach(cust);
  }

Exception raised by the Compiler:

The type arguments for method 'System.Data.Linq.Table(Invoices).AttachAll(TSubEntity)(System.Collections.Generic.IEnumerable(TSubEntity))' cannot be inferred from the usage. Try specifying the type arguments explicitly.

Question: What is the proper way to cast the collection properly? Any other solutions besides a cast?

Answer 1

Tf cust.Invoices already refers to instances of the CustomerInvoices table, just doing db.Customers.Attach(cust); db.Update(); should be all you need to do.

If CustomerInvoices is a different type from Customer.Invoice, you'll probably need to iterate through the collection, and cast each one.

Answer 2

public string Save(Role objRole) { string message = string.Empty; System.Data.Common.DbTransaction trans = null;
try { Objdb.Connection.Open(); trans = Objdb.Connection.BeginTransaction(); Objdb.Transaction = trans; if (objRole.RoleId == 0) { Objdb.Roles.InsertOnSubmit(objRole); } else {
Objdb.Roles.Attach(objRole, true); Objdb.RolePages.AttachAll(objRole.RolePages.Where(a => a.IsNew == false && a.IsDeleted == false), true); Objdb.RolePages.InsertAllOnSubmit(objRole.RolePages.Where(a => a.IsNew == true && a.IsDeleted == false)); Objdb.RolePages.DeleteAllOnSubmit(objRole.RolePages.Where(a => a.IsNew == false && a.IsDeleted == true)); } Objdb.SubmitChanges(); trans.Commit();
message = "Record saved successfully."; } catch (Exception ex) { trans.Rollback(); message = "Error : " + ex.Message; } return message; }

Answer 3

        else if (((CheckBox)item.Cells[2].FindControl("ckbSelect")).Checked == true && ((Label)item.Cells[2].FindControl("lblIsInuse")).Text == "1")
        {
            RolePage objTemp = new RolePage();
            objTemp = new Helper().GetRolePagebyID(roleId, Convert.ToInt32(item.Cells[0].Text));
            rp.RoleId = objTemp.RoleId;
            rp.PageId = objTemp.PageId;
            rp.RolePageId = objTemp.RolePageId;
            rp.CreatedOn = objTemp.CreatedOn;
            rp.Timestamp = objTemp.Timestamp; 
            //rp.RoleId = roleId;
            //rp.PageId = Convert.ToInt32(item.Cells[0].Text);
            //rp.RolePageId =Convert.ToInt32(((Label)item.Cells[2].FindControl("lblRolePageId")).Text.Trim());  
            rp.IsNew = false;
            rp.IsDeleted = false;                
            rp.UpdatedOn = DateTime.Now;  
            erp.Add(rp);               
        }