Error message whenever alphabet is entered rather than number - vb.net

Question

I m new to vb.net & I have a problem that whenever user enters an alphabet he/she will receive message that only numbers are allowed. For this code.... Please help me. I shall be very thankful to you.
Public Class Form1
Private Sub DataGridView1_EditingControlShowing(sender As Object, e As DataGridViewEditingControlShowingEventArgs) Handles DataGridView1.EditingControlShowing
If DataGridView1.CurrentCell.ColumnIndex = 0 Then
Dim combo As ComboBox = CType(e.Control, ComboBox)
If (combo IsNot Nothing) Then
RemoveHandler combo.SelectionChangeCommitted, New EventHandler(AddressOf ComboBox_SelectionChangeCommitted)
AddHandler combo.SelectionChangeCommitted, New EventHandler(AddressOf ComboBox_SelectionChangeCommitted)
End If
End If
End Sub
Private Sub ComboBox_SelectionChangeCommitted(ByVal sender As System.Object, ByVal e As System.EventArgs)
Dim combo As ComboBox = CType(sender, ComboBox)
If combo.SelectedItem = "Item1" Then
DataGridView1.CurrentRow.Cells(1).Value = "KG"
DataGridView1.CurrentRow.Cells(3).Value = "100"
DataGridView1.CurrentRow.Cells(2).Value = "Raw Material"
ElseIf combo.SelectedItem = "Item2" Then
DataGridView1.CurrentRow.Cells(1).Value = "Liter"
DataGridView1.CurrentRow.Cells(3).Value = "47"
DataGridView1.CurrentRow.Cells(2).Value = "Raw Material"
ElseIf combo.SelectedItem = "Item3" Then
DataGridView1.CurrentRow.Cells(1).Value = "Pound"
DataGridView1.CurrentRow.Cells(3).Value = "54"
DataGridView1.CurrentRow.Cells(2).Value = "Raw Material"
End If
End Sub
Private Sub Mul_Button_Click(sender As Object, e As EventArgs) Handles Mul_Button.Click
Dim s As Int16 = Convert.ToInt16(DataGridView1.CurrentRow.Cells(3).Value)
Dim s1 As Int16 = Convert.ToInt16(DataGridView1.CurrentRow.Cells(4).Value)
DataGridView1.CurrentRow.Cells(5).Value = s * s1
End Sub
Private Sub DataGridView1_CellValidated(sender As Object, e As EventArgs) Handles DataGridView1.CellValidated
Dim s As Int16 = Convert.ToInt16(DataGridView1.CurrentRow.Cells(3).Value)
Dim s1 As Int16 = Convert.ToInt16(DataGridView1.CurrentRow.Cells(4).Value)
DataGridView1.CurrentRow.Cells(5).Value = s * s1
If DataGridView1.RowCount > 0 Then
Dim sum As Integer
For index As Integer = 0 To DataGridView1.RowCount - 1
sum += Convert.ToInt32(DataGridView1.Rows(index).Cells(5).Value)
Next
TextBox1.Text = sum
End If
End Sub
Private Sub Add_Button_Click(sender As Object, e As EventArgs) Handles Add_Button.Click
If DataGridView1.RowCount > 0 Then
Dim sum As Integer
For index As Integer = 0 To DataGridView1.RowCount - 1
sum += Convert.ToInt32(DataGridView1.Rows(index).Cells(5).Value)
Next
TextBox1.Text = sum
End If
End Sub
End Class

Answer 1

Either wrap your code that has Convert.ToInt16() calls in them with Try/Catch blocks, or convert them to the Int16.TryParse() approach instead.
For example, this line:
Dim s As Int16 = Convert.ToInt16(DataGridView1.CurrentRow.Cells(3).Value)
Could become:
Dim s As Int16
Dim strValue As String = DataGridView1.CurrentRow.Cells(3).Value
If Int16.TryParse(strValue, s) Then
' ... do something with "s" in here ...
' ... continue with code...
Else
MessageBox.Show(strValue, "Invalid Value")
End If