c# - DbCommand 的自定义可视化工具

Question

您好，我正在尝试为应该在 Visual Studio 2013 中使用的 DbCommand 对象创建自定义可视化工具。

我有以下代码

using VisualizerTest;
using Microsoft.VisualStudio.DebuggerVisualizers;
using System;
using System.Data.Common;
using System.Diagnostics;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Windows.Forms;

[assembly: DebuggerVisualizer(typeof(TestVisualizer), typeof(CommandObjectSource), Target = typeof(DbCommand), Description = "Test")]

namespace VisualizerTest
{
    public class TestVisualizer : DialogDebuggerVisualizer
    {
        protected override void Show(IDialogVisualizerService windowService, IVisualizerObjectProvider objectProvider)
        {
            DbCommand command;
            try
            {
                using (Stream stream = objectProvider.GetData())
                {
                    BinaryFormatter formatter = new BinaryFormatter();
                    command = (DbCommand)formatter.Deserialize(stream);
                }
                MessageBox.Show(command.CommandText);
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }
    }
}


namespace VisualizerTest
{
    [Serializable]
    public class CommandObjectSource : VisualizerObjectSource
    {
        public override void GetData(object target, Stream outgoingData)
        {
            if (target != null && target is DbCommand)
            {
                DbCommand command = (DbCommand)target;

                BinaryFormatter formatter = new BinaryFormatter();

                formatter.Serialize(outgoingData, command);
            }
        }
    }
}

但是 CommandObjectSource 从未被调用，而是我得到一个异常

Microsoft.VisualStudio.DebuggerVisualizers.DebugViewerShim.RemoteObjectSourceException: Type 'System.Data.SqlClient.SqlCommand' in Assembly 'System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.

我的理解是，通过使用自定义 VisualizerObjectSource 我可以解决序列化问题？

作为旁注，我尝试将 Target = typeof(DbCommand) 更改为 Target = typeof(SqlCommand)，但没有任何区别。

测试代码:

class Program
{
    static void Main(string[] args)
    {

        using (SqlCommand command = new SqlCommand("SELECT Field1 FROM table WHERE Field2 = @Value1"))
        {
            command.Parameters.AddWithValue("@Value1", 1338);
            TestValue(command);
        }

        Console.ReadKey();
    }

    static void TestValue(object value)
    {
        VisualizerDevelopmentHost visualizerHost = new VisualizerDevelopmentHost(value, typeof(TestVisualizer));
        visualizerHost.ShowVisualizer();
    }
}

Answer 1

因为您正在显式创建 VisualizerDevelopmentHost，所以它不会使用 DebuggerVisualizerAttribute，因此您必须将 CommandObjectSource 作为第三个参数传递:

VisualizerDevelopmentHost visualizerHost = 
    new VisualizerDevelopmentHost(value, typeof(TestVisualizer),                  
                                         typeof(CommandObjectSource));

通过此更改，您的 CommandObjectSource 将被调用，但您仍然遇到序列化问题，因为 BinaryFormatter 还需要将类标记为 Seralizabe...

因此，您应该只包含 CommandText(或者创建一个新的 DTO 对象并在需要多个属性时将其序列化):

[Serializable]
public class CommandObjectSource : VisualizerObjectSource
{
    public override void GetData(object target, Stream outgoingData)
    {
        if (target != null && target is DbCommand)
        {
            DbCommand command = (DbCommand)target;

            var writer = new StreamWriter(outgoingData);
            writer.WriteLine(command.CommandText);
            writer.Flush();
        }
    }
}

阅读它:

public class TestVisualizer : DialogDebuggerVisualizer
{
    protected override void Show(IDialogVisualizerService windowService, IVisualizerObjectProvider objectProvider)
    {
        string command;
        try
        {
            command = new StreamReader(objectProvider.GetData()).ReadLine();
            MessageBox.Show(command);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
        }
    }
}