title: The name 'sqlDbType' does not exist in the current context
body: <p>I'm going to edit textbox value.. but i saw there's a problem</p>
  
  <pre><code>  protected void btn_edit_Click(object sender, EventArgs e)
      {
          DatabaseConnector con = new DatabaseConnector().CreateInstance();
          SqlCommand com = new SqlCommand("UPDATE tbl_BinCardManager SET ItemName = @ItemName WHERE ItemNo = @ItemNo");
          com.Parameters.Add("@ItemName",sqlDbType.VarChar);
          con.Open();
          cmd.ExecuteNonQuery();
          con.Close();
  
      }
  </code></pre>
  
  <p>ERROR 1:</p>
  
  <blockquote>
    <p>The name 'sqlDbType' does not exist in the current context</p>
  </blockquote>
  
  <p>ERROR 2:</p>
  
  <blockquote>
    <p>'ERPSystem.DatabaseConnector' does not contain a definition for 'Open'
    and no extension method 'Open' accepting a first argument of type
    'ERPSystem.DatabaseConnector' could be found (are you missing a using
    directive or an assembly reference?)</p>
  </blockquote>
  
  <p>My DBConnector Class is :</p>
  
  <pre><code> class DatabaseConnector
  {
      private DatabaseConnector databaseConnector;
      private string connectionString = "Data Source=lernlap;Initial Catalog=ERPSystemDB;User ID=sa;Password=sa123";
  
      public DatabaseConnector()
      {
  
      }
  
      private SqlConnection connection;
  
      private bool Connect()
      {
          try
          {
              connection = new SqlConnection(connectionString);
              connection.Open();
              return true;
          }
          catch(Exception) {
  
              return false;
  
          }
      }
  
      internal DatabaseConnector CreateInstance()
      {
          if (databaseConnector == null)
          {
              databaseConnector = new DatabaseConnector();
              databaseConnector.Connect();
          }
          return databaseConnector;
      }
  </code></pre>