在C#中需要代码说明

Question

我需要逐行详细解释下面的代码以及流程如何,例如,当我调试时.我刚刚在我的程序中使用了这个代码来避免a cross thread access error.代码工作正常,但这段代码是什么呢？

delegate void updateTextField(string Text);
private void updateText(string Text)
{
    if (txtDelegate.InvokeRequired)
    {
        updateTextField del = new updateTextField(updateText);
        txtDelegate.Invoke(del, new object[] { Text });
    }
    else
    {
        txtDelegate.Text = Text;
    }
}

此方法在以下情况下调用backgroundWorker_DoWork():

updateText("using delegate");

我还需要代表们的解释.我读到了它,但我理解的是委托就像一个函数的指针,但我需要一个简单的例子清晰的解释.把我当成新手.

Answer 1

// Declaring a delegate function kind of lifts the function away from the 
// current object and the current thread, making it 'thread-safe' to call 
// (although it may still not be thread-safe to execute).
delegate void updateTextField(string Text); 
private void updateText(string Text)
{
    // This asks the control if it's running on the same thread as this method is 
    // currently executing, i.e. can I update you directly or do I need to use 
    // the cross thread calling method "Invoke".
    if (txtDelegate.InvokeRequired) 
    {
        // Here we define the delegate function that's going to be Invoked. 
        // Here it's the same function were currently within but when it's invoked 
        // by the following line, it'll be done on the same thread as the control. 
        // At that point, InvokeRequired will return false and the other branch 
        // will be followed to update the actual text on the control.
        updateTextField del = new updateTextField(updateText);             

        // Here we invoke the function passing in the Text we want to update the
        // control with as a parameter.
        txtDelegate.Invoke(del, new object[] { Text });         
    }
    else
    {
        // When this function is Invoked, this is the branch that will be followed 
        // (as we're on the same thread as the control) and the text on the control
        //  will be replaced with the text passed in from the Invoke.
        txtDelegate.Text = Text;          
    }
}

我希望更详细地介绍它,委托的实际机制是"线程安全的"超出了这个答案的范围.