How to eliminate multiple Entry

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C#

C#4.0

Telerik

Hello,
I work on Windows c# telerik.
And i have problem that as when i want to add new entry in my grid view it will add 2 entries. in which one is correct but other one will get only 2 fields.
how to eliminate this problem.
I required as only one entry should have entered.
New Entry added as there will form will popup and on save data entry should have enter in GridView


My Code is as below.

public void Save(TimesheetEntry timesheetEntry)
        {
            if (timesheetEntry.TimesheetEntriesId == -1)
            {
                timesheetEntry.SequenceNumber = GetNextSequenceNumber(timesheetEntry.FileId, timesheetEntry.EntryDate);
                Add(timesheetEntry);

            }
            else
            {
                Update(timesheetEntry);
            }
            //Audit trail
            //TODO:
            //MyAuditTrialModel.Add<TimesheetEntry>(Helper.Actions.CU_Timesheet, Helper.TableNames.TimesheetEntry, timesheetEntry);
        }

Thanks in advance