c# - 使用 MySqlBackup.NET 导出数据库时出现异常

Question

我使用以下代码备份 MYSQL 数据库。

    private void button2_Click(object sender, EventArgs e)
    {
        string file = "D:\\backup.sql";
        //string conn = "server=localhost;user=root;pwd=qwerty;database=test;";
        String str = @"server=192.168.1.219;database=abc;userid=sha;password='123';";
        MySqlBackup mb = new MySqlBackup(str);
        mb.ExportInfo.FileName = file;
        mb.Export();
    }

我的堆栈跟踪如下 -

A first chance exception of type 'System.NullReferenceException' occurred in MySqlBackup.dll
System.Transactions Critical: 0 : <TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Critical"><TraceIdentifier>http://msdn.microsoft.com/TraceCodes/System/ActivityTracing/2004/07/Reliability/Exception/Unhandled</TraceIdentifier><Description>Unhandled exception</Description><AppDomain>TestAppMysqlDBConnect.vshost.exe</AppDomain><Exception><ExceptionType>System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType><Message>Object reference not set to an instance of an object.</Message><StackTrace>   at MySql.Data.MySqlClient.MySqlBackup.ExportExecute()
   at MySql.Data.MySqlClient.MySqlBackup.Export()
   at TestAppMysqlDBConnect.Form1.button2_Click(Object sender, EventArgs e) in C:\Users\Shashika\Documents\Visual Studio 2010\Projects\TestAppMysqlDBConnect\TestAppMysqlDBConnect\Form1.cs:line 52
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   ..

但是有一个例外，就是说有一个空引用异常。当我通过 C# 程序将数据传递到数据库时。插入成功，无一例外。此异常仅发生在我尝试通过 C# 程序备份数据库时。我使用了上面链接中的 2 个 Dll 文件。这些是 - MySql.Data.dll MySqlBackup.dll

我无法解决这个异常。请帮忙。

Answer 1

尝试使用此功能（不要忘记您必须将 MySqlBackup.dll 添加到您的项目引用中）：

public void Backup()
    {
        try
        {
            // Backup...
            DateTime Time = DateTime.Now;
            year = Time.Year;
            month = Time.Month;
            day = Time.Day;
            hour = Time.Hour;
            minute = Time.Minute;
            second = Time.Second;
            millisecond = Time.Millisecond;

            //Save file to Path with the current date as a filename
            string path;
            path = txb_Path.Text + year + "-" + month + "-" + day + "--" + hour + "-" + minute + "-" + second + ".sql";
            string file = path;
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand())
                {
                    using (MySqlBackup mb = new MySqlBackup(cmd))
                    {
                        cmd.Connection = conn;
                        conn.Open();
                        mb.ExportToFile(file);
                        conn.Close();
                    }
                }
            }
            //Done----
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error , unable to backup!" + ex.Message);
        }
    }