C# 调用任何跨线程代码的最佳方式？

Best Way to Invoke Any Cross-Threaded Code?

提问by CLaRGe

I know that this question has been asked before, but I'm looking for a way to:

我知道以前有人问过这个问题，但我正在寻找一种方法：

1. streamline the creation of safe cross-threaded code.
2. reuse this code in any situation (no Windows Forms references).

1. 简化安全跨线程代码的创建。
2. 在任何情况下重用此代码（无 Windows 窗体引用）。

Here's what I have so far, but I want to remove the Windows Forms references. Any ideas?

到目前为止，这是我所拥有的，但我想删除 Windows 窗体引用。有任何想法吗？

public delegate void SafeInvokeDelegate(System.Action action);
public class SafeInvoke
{
    private readonly System.Windows.Forms.Control _threadControl;

    public SafeInvoke()
    {
        _threadControl = new System.Windows.Forms.Control();
    }

    public void Invoke(System.Action action)
    {
        if (_threadControl.InvokeRequired)
            _threadControl.Invoke(new SafeInvokeDelegate(Invoke), new object[] {action});
        else if (action != null) action();
    }
}

The above class might be used this way:

上面的类可以这样使用：

SafeInvoke _safeInvoker = new SafeInvoke();
void SafeClearItems()
{
    _safeInvoker.Invoke(delegate
        {
            listView1.Items.Clear();
        });
}

How would I remove the System.Windows.Forms.Control in the SafeInvoke class but keep the same functionality?

如何删除 SafeInvoke 类中的 System.Windows.Forms.Control 但保持相同的功能？

采纳答案by Samuel

You also could use an extension method and lambdas to make your code much cleaner.

您还可以使用扩展方法和 lambdas 使您的代码更简洁。

using System.ComponentModel;
public static class ISynchronizeInvokeExtensions
{
  public static void InvokeEx<T>(this T @this, Action<T> action) where T : ISynchronizeInvoke
  {
    if (@this.InvokeRequired)
    {
      @this.Invoke(action, new object[] { @this });
    }
    else
    {
      action(@this);
    }
  }
}

So now you can use InvokeExon any ISynchronizeInvoke and be able to access the properties and fields of implementing class.

所以现在您可以InvokeEx在任何 ISynchronizeInvoke 上使用并能够访问实现类的属性和字段。

this.InvokeEx(f => f.listView1.Items.Clear());

回答by Jon Skeet

Use ISynchronizeInvokeinstead of Control. That's the interface that Controlimplements with Invoke/BeginInvoke/EndInvoke/InvokeRequired.

使用ISynchronizeInvoke代替Control。这是Control实现 with的接口Invoke/BeginInvoke/EndInvoke/InvokeRequired。

An alternative is to use SynchronizationContext.Current- which is what BackgroundWorkeruses, I believe.

另一种选择是使用SynchronizationContext.Current-BackgroundWorker我相信这就是使用。

回答by Eyal

Here it is in VB.net, very similar to Samuel's answer. I have four overloads depending on whether you want a subroutine or function and whether or not there's a parameter. It would be easy to add more overloads for more parameters. VB.Net is able to infer the types.

这是在 VB.net 中，与 Samuel 的回答非常相似。我有四个重载，具体取决于您想要子例程还是函数以及是否有参数。为更多参数添加更多重载会很容易。VB.Net 能够推断类型。

Module ISynchronizeInvokeExtensions
    Public Delegate Function GenericLambdaFunctionWithParam(Of InputType, OutputType)(ByVal input As InputType) As OutputType
    Private Delegate Function InvokeLambdaFunctionCallback(Of InputType, OutputType)(ByVal f As GenericLambdaFunctionWithParam(Of InputType, OutputType), ByVal input As InputType, ByVal c As System.ComponentModel.ISynchronizeInvoke) As OutputType
    Public Function InvokeEx(Of InputType, OutputType)(ByVal f As GenericLambdaFunctionWithParam(Of InputType, OutputType), ByVal input As InputType, ByVal c As System.ComponentModel.ISynchronizeInvoke) As OutputType
        If c.InvokeRequired Then
            Dim d As New InvokeLambdaFunctionCallback(Of InputType, OutputType)(AddressOf InvokeEx)
            Return DirectCast(c.Invoke(d, New Object() {f, input, c}), OutputType)
        Else
            Return f(input)
        End If
    End Function

    Public Delegate Sub GenericLambdaSubWithParam(Of InputType)(ByVal input As InputType)
    Public Sub InvokeEx(Of InputType)(ByVal s As GenericLambdaSubWithParam(Of InputType), ByVal input As InputType, ByVal c As System.ComponentModel.ISynchronizeInvoke)
        InvokeEx(Of InputType, Object)(Function(i As InputType) As Object
                                           s(i)
                                           Return Nothing
                                       End Function, input, c)
    End Sub

    Public Delegate Sub GenericLambdaSub()
    Public Sub InvokeEx(ByVal s As GenericLambdaSub, ByVal c As System.ComponentModel.ISynchronizeInvoke)
        InvokeEx(Of Object, Object)(Function(i As Object) As Object
                                        s()
                                        Return Nothing
                                    End Function, Nothing, c)
    End Sub

    Public Delegate Function GenericLambdaFunction(Of OutputType)() As OutputType
    Public Function InvokeEx(Of OutputType)(ByVal f As GenericLambdaFunction(Of OutputType), ByVal c As System.ComponentModel.ISynchronizeInvoke) As OutputType
        Return InvokeEx(Of Object, OutputType)(Function(i As Object) f(), Nothing, c)
    End Function
End Module

Usage (run this in a backgroundworker):

用法（在后台工作中运行）：

    InvokeEx(Sub(x As String) Me.Text = x, "foo", Me) 'set form title to foo
    InvokeEx(AddressOf MsgBox, Me.Text, Me)
    InvokeEx(Sub() Me.Text &= "!", "foo", Me) 'append "!" to form title
    InvokeEx(AddressOf MsgBox, Me.Text, Me)
    Dim s As String = InvokeEx(Function() Me.Text, Me) & "bar" 'get form title to backgorundworker thread
    InvokeEx(AddressOf MsgBox, s, Me) 'display the string from backgroundworker thread

回答by Shawn Kovac

here's the VB equivalent code to Samuel's answer that i use. notice i actually have 2 extensions functions, but i must admit i don't know why they are there. i copied my C# version years ago (maybe from this site) and it had both extension functions, but for what reason, i don't fully understand. i just copied it and how to use it, and i half understand all that goes on 'under the hood' with these complicated functions.

这是我使用的 Samuel 答案的 VB 等效代码。注意我实际上有 2 个扩展功能，但我必须承认我不知道它们为什么在那里。我几年前复制了我的 C# 版本（可能来自这个站点）并且它具有两个扩展功能，但是出于什么原因，我不完全理解。我只是复制了它以及如何使用它，而且我对这些复杂功能“幕后”发生的所有事情都了解一半。

#Const System_ComponentModel = True
#Const System_Drawing = False

Option Compare Binary
Option Explicit On
Option Strict On

Imports System.Collections
Imports System.Runtime.CompilerServices ' for Extension() attribute
Imports System.Text
#If System_ComponentModel Then
Imports System.ComponentModel
#End If
#If System_Drawing Then
Imports System.Drawing
#End If

Public Module MyExtensions

    ' other #Region blocks are removed. i use many in my Extensions
    ' module/class. the below code is only the 2 relevant extension
    ' for this 'SafeInvoke' functionality. but i use other regions
    ' such as "String extensions" and "Numeric extensions". i use
    ' the above System_ComponentModel and System_Drawing compiler
    ' directives to include or exclude blocks of code that i want
    ' to either include or exclude in a project, which allows me to
    ' easily compare my code in one project with the same file in
    ' other projects to syncronise new changes across projects.
    ' you can scrap pretty much all the code above,
    ' but i'm giving it here so you see it in the full context.

    #Region "ISynchronizeInvoke extensions"

    #If System_ComponentModel Then

        <Extension()>
        Public Function SafeInvoke(Of T As ISynchronizeInvoke, TResult)(isi As T, callFunction As Func(Of T, TResult)) As TResult
            If (isi.InvokeRequired) Then
                Dim result As IAsyncResult = isi.BeginInvoke(callFunction, New Object() {isi})
                Dim endresult As Object = isi.EndInvoke(result)
                Return DirectCast(endresult, TResult)
            Else
                Return callFunction(isi)
            End If
        End Function

        ''' <summary>
        ''' This can be used in VB with:
        ''' txtMyTextBox.SafeInvoke(Sub(d) d.Text = "This is my new Text value.")
        ''' or:
        ''' txtMyTextBox.SafeInvoke(Sub(d) d.Text = myTextStringVariable)
        ''' </summary>
        ''' <typeparam name="T"></typeparam>
        ''' <param name="isi"></param>
        ''' <param name="callFunction"></param>
        ''' <remarks></remarks>
        <Extension()>
        Public Sub SafeInvoke(Of T As ISynchronizeInvoke)(isi As T, callFunction As Action(Of T))
            If isi.InvokeRequired Then
                isi.BeginInvoke(callFunction, New Object() {isi})
            Else
                callFunction(isi)
            End If
        End Sub

    #End If

    #End Region

    ' other #Region blocks are removed from here too.

End Module

And the C# version is:

而 C# 版本是：

#define System_ComponentModel
#undef  System_Drawing

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

#if System_ComponentModel
using System.ComponentModel;
#endif
#if System_Drawing
using System.Drawing;
#endif

namespace MyCompany.Extensions
{
    static partial class MyExtensions
    {

        // other #Region blocks are removed. i use many in my Extensions
        // module/class. the below code is only the 2 relevant extension
        // for this 'SafeInvoke' functionality. but i use other regions
        // such as "String extensions" and "Numeric extensions". i use
        // the above System_ComponentModel and System_Drawing compiler
        // directives to include or exclude blocks of code that i want
        // to either include or exclude in a project, which allows me to
        // easily compare my code in one project with the same file in
        // other projects to syncronise new changes across projects.
        // you can scrap pretty much all the code above,
        // but i'm giving it here so you see it in the full context.

        #region ISynchronizeInvoke extensions
#if System_ComponentModel

        public static TResult SafeInvoke<T, TResult>(this T isi, Func<T, TResult> callFunction) where T : ISynchronizeInvoke
        {
            if (isi.InvokeRequired)
            {
                IAsyncResult result = isi.BeginInvoke(callFunction, new object[] { isi });
                object endResult = isi.EndInvoke(result); return (TResult)endResult;
            }
            else
                return callFunction(isi);
        }

        /// <summary>
        /// This can be used in C# with:
        /// txtMyTextBox.SafeInvoke(d => d.Text = "This is my new Text value.");
        /// or:
        /// txtMyTextBox.SafeInvoke(d => d.Text = myTextStringVariable);
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="isi"></param>
        /// <param name="callFunction"></param>
        public static void SafeInvoke<T>(this T isi, Action<T> callFunction) where T : ISynchronizeInvoke
        {
            if (isi.InvokeRequired) isi.BeginInvoke(callFunction, new object[] { isi });
            else
                callFunction(isi);
        }

#endif
        #endregion

        // other #Region blocks are removed from here too.

    } // static class MyExtensions

} // namespace

Happy coding!

快乐编码！

回答by Tj Laubscher

Nowadays it's easy to Invoke.
e.g. Say we want to invoke a Label(lblVal) to get value of txtVal

现在很容易调用。
例如，假设我们要调用一个 Label(lblVal) 来获取 txtVal 的值

lblVal.Invoke((MethodInvoker)delegate{lblVal.Text = txtVal.Text;});

...it's as easy as that :D

...就这么简单：D