Option Strict On
Option Explicit On
Option Infer Off
Option Compare Text
 
Public Class Form1
    Dim DT As New System.Data.DataTable
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) _
      Handles MyBase.Load
        DT.CaseSensitive = True
        DT.Columns.Add("Text1", GetType(System.String))
        DT.Columns.Add("Text2", GetType(System.String))
        DT.Columns.Add("PKText", GetType(System.String))
        DT.Columns.Add("PKSpacesLeft", GetType(System.Int32))
        DT.Columns.Add("PKSpacesRight", GetType(System.Int32))
        DT.Constraints.Add("PK", {DT.Columns(2), DT.Columns(3), DT.Columns(4)}, _
          True)
 
        Dim DGV As New DataGridView
        DGV.Dock = DockStyle.Fill
        DGV.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill
        Me.Controls.Add(DGV)
        DGV.DataSource = DT
        DGV.Columns(2).Visible = False
        DGV.Columns(3).Visible = False
        DGV.Columns(4).Visible = False
 
        AddRow(DT, "Text1", "Text2") ' OK
        AddRow(DT, " Text1", " Text2") ' OK
        AddRow(DT, "Text1 ", "Text2 ") ' OK
        AddRow(DT, "Text1 ", "Text2 ") ' ErrMsg - duplicates!
    End Sub
    Private Sub AddRow(Table As DataTable, Text1 As String, Text2 As String)
        If Not Text1 = String.Empty Then
            Dim TT As String = Trim(Text1) ' trimmed text
            Dim SL As Integer = Text1.IndexOf(TT) ' spaces left
            Dim SR As Integer = Text1.Length - SL - TT.Length ' spaces right
            Try
                DT.Rows.Add(Text1, Text2, TT, SL, SR)
            Catch ex As System.Data.ConstraintException
                If DirectCast(ex.TargetSite, System.Reflection.MethodInfo).Name _
                  = "CheckConstraint" Then
                    MsgBox(ex.Message, MsgBoxStyle.Exclamation)
                End If
            End Try
        Else
            MsgBox("Text1 is empty!", MsgBoxStyle.Critical) ' Write log, dont 
            ' show Msg
        End If
    End Sub
End Class