[سعود]

وهذا كلاس الفورم بشكل كامل
استخدمت دالة تلافيا لتكرار الكود في حال احببت وضعه باكثر من مكان

كود :

Imports System.Data.OleDb

Public Class Form1
    Dim str As String = "provider=microsoft.ace.oledb.12.0;data source=|datadirectory|\db.accdb"
    Dim con As New OleDbConnection(str)
    Sub gd()
        Dim ds As New DataSet
        Dim da As New OleDbDataAdapter("select tn from tb", con)
        ds.Clear()
        d.DataSource = Nothing

        da.Fill(ds, "tb")

        d.DataSource = ds
        d.DataMember = "tb"
        If con.State = ConnectionState.Open Then
            con.Close()
        End If

    End Sub

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        My.Settings.m = Me.Location
        My.Settings.Save()
    End Sub
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Location = My.Settings.m
        gd()
    End Sub
    Function isfound(ByVal t As String) As Boolean
        Dim sql As New OleDbCommand("select count(tn) from tb where tn=@tn", con)
        sql.Parameters.AddWithValue("@tn", t)

        If con.State = ConnectionState.Closed Then
            con.Open()
        End If
        If sql.ExecuteScalar > 0 Then
            ' MsgBox("الاسم موجود", MsgBoxStyle.Critical, "")
            Return True
        Else
            Return False
        End If
        gd()
        If con.State = ConnectionState.Open Then
            con.Close()
        End If
    End Function
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        If TextBox1.Text.Trim.Replace(" ", "").Length < 2 Then Exit Sub
        If insert(TextBox1.Text) Then
            MsgBox("الاسم موجود", MsgBoxStyle.Critical, "")
        Else
            MsgBox("تم الحفظ", MsgBoxStyle.Information, "")
        End If
    End Sub
    Function insert(ByVal t As String) As Boolean
        If isfound(t) Then
            Return True
        Else
            Dim se As New OleDbCommand("insert into tb(tn) values(@tn)", con)
            se.Parameters.AddWithValue("@tn", t)
            If con.State = ConnectionState.Closed Then
                con.Open()
            End If
            Try
                se.ExecuteNonQuery()
                Return False
            Catch ex As Exception
                Return True
            End Try


        End If
        gd()
        If con.State = ConnectionState.Open Then
            con.Close()
        End If

    End Function
    
End Class