select the first row in datagridview

 Private Sub DataGridView1_CellContentClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
        Dim i As Integer


        i = DataGridView1.CurrentRow.Index


        'Me.AxAcroPDF1.src = DataGridView1.Item(0, i).Value


        If Me.DataGridView1.CurrentCell.ColumnIndex = 1 Then
            Me.AxAcroPDF1.src = DataGridView1.Item(1, i).Value
        End If


        If Me.DataGridView1.CurrentCell.ColumnIndex = 2 Then
            Me.AxAcroPDF1.src = DataGridView1.Item(2, i).Value
        End If


        If Me.DataGridView1.CurrentCell.ColumnIndex = 3 Then
            Me.AxAcroPDF1.src = DataGridView1.Item(3, i).Value
        End If
        If Me.DataGridView1.CurrentCell.ColumnIndex = 4 Then
            Me.AxAcroPDF1.src = DataGridView1.Item(4, i).Value
        End If
        If Me.DataGridView1.CurrentCell.ColumnIndex = 5 Then
            Me.AxAcroPDF1.src = DataGridView1.Item(5, i).Value
        End If


    End Sub



Note: You can use 

Me.TextBox.Text = DataGridView1.Item(1, i).Value
                          Or
Me.Label1.Text = DataGridView1.Item(4, i).Value