Question

All I want to do is to check for textboxes with string value if yes then the message box will appear saying (use number).

    For Each t In Me.Controls
        If TextBox1.Text = (String) Then
            MsgBox("Please Use Number")
            Exit Sub
            Exit For
        End If
    Next

Thanks in advance

Answer 1

From your error-message i assume that you want to validate that the user entered a numerical value. Then you can either use Int32.TryParse or Double.TryParse or simply enumerate all chars and check if they are digits:

For Each txt In Me.Controls.OfType(Of textBox)()
    Dim allDigit = txt.Text.Trim.Length <> 0 AndAlso _
            txt.Text.All(Function(chr) Char.IsDigit(chr))
    If Not allDigit Then
        MsgBox("Please Use Number")
        Exit Sub
    End If
Next

With Int32.TryParse:

Dim intVal As Int32
Dim isInteger As Boolean = Int32.TryParse(txt.Text, intVal)

(assuming also that you want to validate all TextBoxes on your form)