يوجد مشكلة عند تحميل البيانات فى كمبوبوكس داخل داتا جريد

كود :
Imports System.Data.SqlClient



Public Class Form1

    Dim dtUint As New DataTable

    'comboBox Add Item

    Public query As String

    Public command As SqlCommand

    Public reader As SqlDataReader

    'Public conn As New SqlConnection("Data Source=.\SQLEXPRESS;Initial Catalog=Accounts;Integrated Security=True")



    Public conn As New SqlConnection("Data Source=.;Initial Catalog=Accounts;Integrated Security=True")



    Private Function GetData(ByVal sql As String) As DataTable



        Dim cmd As SqlCommand = New SqlCommand(sql, conn)

        cmd.CommandType = CommandType.Text

        Dim sda As SqlDataAdapter = New SqlDataAdapter(cmd)

        Dim dt As DataTable = New DataTable

        sda.Fill(dt)

        Return dt

    End Function



    Private Sub AddUint_Combo()



        Dim sda As New SqlDataAdapter("SELECT * FROM Uint_NameTbl", conn)

        sda.Fill(dtUint)

        With TryCast(dvg_purchas.Columns(2), DataGridViewComboBoxColumn)

            .DataSource = dtUint

            .DisplayMember = "UintName"

            .ValueMember = "id"

        End With



        Dim dt As New DataTable

        sda.Fill(dt)

        With txtUintName

            .DataSource = dt

            .DisplayMember = "UintName"

            .ValueMember = "id"

        End With





        'Next

    End Sub







    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        AddUint_Combo()

    End Sub

    Public Sub AddItemList()





        'Try

        ' لاضافة بيانات الصنف الى الجريد 

        'If e.KeyCode = Keys.Enter Then

        For i As Integer = 0 To dvg_purchas.Rows.Count - 1

            If txtbarCode.Text = dvg_purchas.Rows(i).Cells(2).Value Then

                '  فى حالة الغاء عملية تعديل واضافة البيانات على اللى موجود سابقا / هيتم ادراج اخر البيانات و تجاهل البيانات السابقة

                If MessageBox.Show("  اضغط نعم لتعديل السعر/ تم إدراج الصنف من قبل هل تريد التعديل ", "اسم الصنف / خطاء تكرار البيانات :" + dvg_purchas.CurrentRow.Cells(2).Value, MessageBoxButtons.YesNo) = Windows.Forms.DialogResult.Yes Then

                    dvg_purchas.Rows(i).Cells(3).Value = txtQuty.Text

                    dvg_purchas.Rows(i).Cells(4).Value = txtPrice.Text



                    Exit Sub

                End If

                ' فى حالة  وجود نفس البيانات بيتم التعديل عليها

                'dvg_purchas.Rows(i).Cells(9).Value = Val(dvg_purchas.Rows(i).Cells(9).Value) + Val(txtQuty.Text)  '  تعديل الكمية

                'dvg_purchas.Rows(i).Cells(10).Value = Val(dvg_purchas.Rows(i).Cells(8).Value) * Val(dvg_purchas.Rows(i).Cells(9).Value)

                'dvg_purchas.Rows(i).Cells(12).Value = Val(dvg_purchas.Rows(i).Cells(10).Value) - Val(dvg_purchas.Rows(i).Cells(11).Value)   '  تعديل اجمالي صافي سعر الشراء





                Exit Sub

            End If

        Next



        dvg_purchas.Rows.Add()

        dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(0).Value = txtbarCode.Text '    

        dvg_purchas.Columns(0).Width = 60

        dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(1).Value = txtitmName.Text '  

        dvg_purchas.Columns(1).Width = 100

        'dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(2).Value = txtUintName.Text  '    

        dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(2).Value = txtUintName.SelectedValue  '    

        dvg_purchas.Columns(2).Width = 80

        dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(3).Value = txtQuty.Text '   

        'dvg_purchas2.Columns(5).Width = 80

        dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(4).Value = txtPrice.Text



        ''dvg_purchas2.Columns(6).Width = 60

        ''dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(7).Value = txtUintName.Text ' الوحدة

        ''dvg_purchas2.Columns(7).Width = 80

        'dvg_purchas.Rows(dvg_purchas.Rows.Count - 1).Cells(8).Value = txtPurchas.Text ' س الشراء

        ''dvg_purchas2.Columns(8).Width = 60



        dvg_purchas_CellEndEdit(dvg_purchas, New DataGridViewCellEventArgs(2, dvg_purchas.Rows.Count - 1))



        'Catch ex As Exception

        '    MsgBox(ex.Message)

        '    conn.Close()

        'End Try

    End Sub







    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

        AddItemList()

    End Sub



    'Private Sub txtUintName_DropDown(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtUintName.DropDown

    '    Try

    '        txtUintName.Items.Clear()



    '        'فحص الاتصال بقاعدة البيانات

    '        If conn.State = ConnectionState.Closed Then conn.Open()

    '        'query = "SELECT [AccountName] FROM Uint_NameTbl where [AccountCategory] ='uint '"

    '        query = "SELECT [UintName] FROM Uint_NameTbl "

    '        ''''' '" + txtInvType2.Text + "'"

    '        Command = New SqlCommand(query, conn)

    '        reader = Command.ExecuteReader()

    '        If reader.HasRows Then

    '            While reader.Read()

    '                txtUintName.Items.Add(reader(0))



    '            End While

    '        End If

    '        reader.Close()

    '        conn.Close()

    '    Catch ex As Exception

    '        MsgBox("The vindName entered is not identical.", MsgBoxStyle.Information + MsgBoxStyle.OkOnly, "Error: Unidentical txtVinName_DropDown")



    '        MsgBox(ex.Message)

    '        conn.Close()

    '    End Try

    'End Sub





    Private Sub dvg_purchas_CellEndEdit(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles dvg_purchas.CellEndEdit

        If conn.State = ConnectionState.Closed Then

            conn.Open()

        End If

        'Dim a = dvg_purchas.CurrentRow.Index

        Dim a = e.RowIndex

        Dim dt As New DataTable

        dt.Clear()

        Dim s As String = dvg_purchas.Rows(a).Cells(2).Value

        Dim ADP As New SqlDataAdapter("select id ,UintID,UintName,UintQty from Uint_NameTbl where id='" & s & "' ", conn)

        ADP.Fill(dt)

        conn.Close()



        If dt.Rows.Count > 0 Then

            'dvg_purchas.Rows(a).Cells("UintName").Value = dt.Rows(0)("UintQty").ToString

            dvg_purchas.Rows(a).Cells(3).Value = dt.Rows(0)("UintQty").ToString

        End If

    End Sub

End Class