Отображение данных столбца DataGridView в ComboBox

TextBox1.Text = Me.DataGridView1.Rows(0).Cells(0).Value
ComboBox1.Text = Me.DataGridView1.Rows(0).Cells(1).Value

    For i = 0 to Me.DataGridView1.Rowcount - 1
          ComboBox1.Items.Add(Me.DataGridView1.Rows(i).Cells(0).Value)
    Next i

IsNothing

     For i = 0 to Me.DataGridView1.Rowcount - 2
          ComboBox1.Items.Add(Me.DataGridView1.Rows(i).Cells(0).Value)
    Next i

if Not IsNothing(Me.DataGridView1.Rows(i).Cells(0).Value) then ComboBox1.Items.Add(Me.DataGridView1.Rows(i).Cells(0).Value)

      For i = 0 to Me.DataGridView1.Rowcount - 2
          If ComboBox1.Text = Me.DataGridView1.Rows(i).Cells(0).Value then 
               TextBox1.Text = Me.DataGridView1.Rows(i).Cells(1).Value
               Exit For
          End If
      Next i

    Private Sub ComboBox1_SelectedIndexChanged(sender As System.Object, e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        For i = 0 To Form2.DataGridView1.RowCount - 2
            If ComboBox1.Text = Form2.DataGridView1.Rows(i).Cells(0).Value Then
                TextBox1.Text = Form2.DataGridView1.Rows(i).Cells(1).Value
                Exit For
            End If
        Next i
    End Sub

For i = 0 to Me.DataGridView1.Rowcount - 1
          ComboBox1.Items.Add(Me.DataGridView1.Rows(i).Cells(0).Value)
    Next i

        Dim CR As String
        For i = 0 To Me.DataGridView1.RowCount - 2
            CR = DataGridView1(0, i).Value
            If Not ComboBox1.Items.Contains(CR) Then ComboBox1.Items.Add(CR)
        Next i

Dim col As Integer = 0
Dim ss = ((From cc As DataGridViewRow In DataGridView1.Rows Where cc.Cells(col).Value IsNot Nothing Select cc.Cells(col).Value).Distinct).ToArray
ComboBox1.Items.AddRange(ss)

        For i = 0 To Me.DataGridView1.Rows.Count - 2
            Dim CR As String = DataGridView1.Item(0, i).Value
            Dim НАШЛА As Boolean = False
             For i2 = 0 To Me.ComboBox1.Items.Count - 1
               If Me.ComboBox1.Items(i2) = CR Then
                   НАШЛА = True
                   Exit For
               End If
             Next i2
        If Not НАШЛА Then Me.ComboBox1.Items.Add(CR)
        Next i