由於連線到外部伺服器是不可預測的，因此在您的 .NET 應用程式中新增錯誤處理非常重要。當連線時發生錯誤時，MySqlConnection 類別會傳回 MySqlException 物件。此物件有兩個屬性在處理錯誤時很有用

在處理錯誤時，您可以根據錯誤編號調整應用程式的回應。連線時最常見的兩個錯誤編號如下

下列程式碼範例示範如何根據實際錯誤管理應用程式的回應

C# 範例

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;

myConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test";

try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection(myConnectionString);
    conn.Open();
}
    catch (MySql.Data.MySqlClient.MySqlException ex)
{
    switch (ex.Number)
    {
        case 0:
            MessageBox.Show("Cannot connect to server.  Contact administrator");
            break;
        case 1045:
            MessageBox.Show("Invalid username/password, please try again");
            break;
    }
}

Visual Basic 範例

Dim myConnectionString as String

myConnectionString = "server=127.0.0.1;" _
          & "uid=root;" _
          & "pwd=12345;" _
          & "database=test"

Try
    Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
    conn.Open()
Catch ex As MySql.Data.MySqlClient.MySqlException
    Select Case ex.Number
        Case 0
            MessageBox.Show("Cannot connect to server. Contact administrator")
        Case 1045
            MessageBox.Show("Invalid username/password, please try again")
    End Select
End Try

MySqlConnection myConnection = new MySqlConnection("server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;Charset=latin1");