title: How to use MySqlHelper.UpdateDataSet
body: <p>I've searched around the web looking for samples on how to use <code>MySqlHelper.UpdateDataSet</code> but all I've found is:</p>
  
  <pre><code>Public Shared Sub UpdateDataSet( _
     ByVal connectionString As String, _
     ByVal commandText As String, _
     ByVal ds As DataSet, _
     ByVal tablename As String _
  ) 
  </code></pre>
  
  <p>I'll be grateful if someone will give me:  </p>
  
  <ul>
  <li>an example of <code>commandText</code> because I didn't understand what kind of command I need to give; </li>
  <li>an explanation of <code>tablename</code> because I need to know if is the name of a table of the DB or of the DataSet or both (with the same name);</li>
  <li>a vb.net code example (to start testing).</li>
  </ul>
  
  <p>I tryed to use the command this way:</p>
  
  <pre><code>Private Sub Btn_Mod_Dataset_Click(sender As Object, e As EventArgs) Handles Btn_Mod_Dataset.Click
      Dim SqlStr$ = "SELECT * FROM MyTest.Users"
      Using DS_Test As DataSet = DB_Functions.mQuery(SqlStr)
          With DS_Test
              .Tables(0).TableName = "Users"
              Dim User$ = .Tables(0).Rows(0)("UserName").ToString
              MsgBox(User)
              .Tables(0).Rows(0)("User") = "Upd_Test"
              User = .Tables(0).Rows(0)("UserName").ToString
              MsgBox(User)
          End With
          Dim DB_Name = "MyTest"
          Dim connectionString$ = "datasource=localhost;username=" + UserDB _ 
              + ";password=" + Password + ";database=" + DB_Name
          MySqlHelper.UpdateDataSet(connectionString, _
              "Update MyTest.Users Set UserName = 'Test_Ok' WHERE UserName = 'Steve'", _
              DS_Test, "Users")
      End Using
  End Sub
  </code></pre>
  
  <p>This gives me </p>
  
  <blockquote>
    <p>System.NullReferenceException' in System.Data.dll</p>
  </blockquote>
  
  <p><strong>EDIT</strong> (to explain my code):<br>
  a) <code>DB_Functions</code> is a sepate class where I've stored some function to use on a MySql DataBase. <code>mQuery</code> is a function who extract query result into a dataset;<br>
  b) 'User' is a field Name : I've changed it to 'UserName' but same result;</p>
  
  <p>d) The code between <code>With</code> and <code>End With</code> is just a test to see what happens;</p>
  
  <p>NOTE that the code gives error but my DB is updated as in the <code>commandText</code> String. I don't understand what happens</p>