Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        For i As Integer = 0 To Me.DataGridView1.RowCount - 2

            For j As Integer = i + 1 To Me.DataGridView1.RowCount - 2
                If DataGridView1.Rows(i).Cells(0).Value = DataGridView1.Rows(j).Cells(0).Value Then
                    DataGridView1.Rows.Remove(DataGridView1.Rows(i))

                End If
            Next
        Next
    End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Me.DataGridView1.AllowUserToAddRows = True 'Satir ekleme olayini iptal eder ayarlardaki
        Dim satır = DataGridView1.Rows.Count - 1
        Dim x As Integer = 0
        While x < satır - 1
            For y As Integer = (satır - 1) To (x + 1) Step -1
                If DataGridView1.Rows(x).Cells(0).Value.ToString() = DataGridView1.Rows(y).Cells(0).Value.ToString() Then
                    DataGridView1.Rows.Remove(DataGridView1.Rows(y))
                    satır -= 1
                End If
            Next
            x += 1
        End While
        Me.DataGridView1.AllowUserToAddRows = False
    End Sub