connexion à mysql

Bonjour,
ce code marche et il affiche tous les utilisateurs mais je voudrais alerter
par msgbox qu'un même pseudo ne peut s'inscrire deux fois

Code:

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Dim conv As New MySqlConnection
    Dim result As Integer
    'MySqlCommand It represents a SQL statement to execute against a MySQL Database
    Dim cmdv As New MySqlCommand
    'Represents a set of data commands and a database connection that 
    'are used to fill a dataset and update a MySQL database. This class cannot be inherited.
    Dim dan As New MySqlDataAdapter
 
 
  Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
try
 
        conv.ConnectionString = ("server=192.168.1.24;user id=keunene;password=;database=activation")
        Try
            conv.Open()
 
            cmdv.Connection = conv
            'in this query it does simply selecting or getting all the user found in the database.
            cmdv.CommandText = "Select * from users where  pseudo  ='" & TextBox3.Text & "'  "
 
 
 
 
 
        Catch ex As Exception
            MsgBox(ex.Message)
 
 
        End Try
        conv.Close()
        dan.Dispose()
        filltable(dtguser)
    End Sub

je voudrais ajouter une condition de ce genre

Code:

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Dim ds As New DataSet
 
                If da.Fill(ds, "login") Then
 
                    MsgBox("Ce code existe déjà dans notre base")
 
end if

merci d'avance

Regarde ce que retourne cette requête :

Code:

SELECT count(*) From Users where pseudo='xxxxxxx'

Si la requête te renvoie 0, tu as un nouveau pseudo

merci de m'avoir ouvert les yeux