从UI线程强制更新GUI

myControlName.Refresh()是在进行“相对长时间运行操作”之前更新控件的简单解决方案。

来源：https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.control.update?view=windowsdesktop-6.0 有两种重绘窗体及其内容的方式：

1. 您可以使用Invalidate方法的一个重载与Update方法一起使用。
2. 您可以调用Refresh方法，强制控件重新绘制自己和所有子控件。这相当于将Invalidate方法设置为true并与Update一起使用。

Invalidate方法控制何时绘制或重绘。Update方法控制何时进行绘制或重绘。如果您不使用Refresh而是将Invalidate和Update方法一起使用，则重绘的内容取决于您使用哪个Invalidate方法的重载。Update方法只是强制控件立即绘制，但是当您调用Update方法时，Invalidate方法控制要绘制什么。

我遇到了与属性Enabled相同的问题，我发现它引发了一个first chance exception，因为它不是线程安全的。我在这里找到了关于“如何从另一个线程更新C#中的GUI？”的解决方案https://dev59.com/wnRB5IYBdhLWcg3wUVtd#661706，并且它有效！

当我想要在“实时”（或基于数据更新或长时间运行的操作）中更新UI时，我使用一个辅助函数来“简化”代码（尽管这里可能看起来有些复杂，但它可以很好地扩展）。以下是我用于更新UI的代码示例：

    // a utility class that provides helper functions
    // related to Windows Forms and related elements
    public static class FormsHelperFunctions {

        // This method takes a control and an action
        // The action can simply be a method name, some form of delegate, or it could be a lambda function (see: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/lambda-expressions)
        public static void InvokeIfNeeded(this Control control, Action action)
        {

            // control.InvokeRequired checks to see if the current thread is the UI thread,
            // if the current thread is not the UI thread it returns True - as in Invoke IS required
            if(control.InvokeRequired)
            {
                // we then ask the control to Invoke the action in the UI thread
                control.Invoke(action);
            }
            // Otherwise, we don't need to Invoke
            else
            {
                // so we can just call the action by adding the parenthesis and semicolon, just like how a method would be called.
                action();
            }
        }

    }

    // An example user control
    public class ExampleUserControl : UserControl {

        /*
            //
            //*****
            // declarations of label and other class variables, etc.
            //*****
            //




            ...
        */

        // This method updates a label, 
        // executes a long-running operation, 
        // and finally updates the label with the resulting message.
        public void ExampleUpdateLabel() {

            // Update our label with the initial text
            UpdateLabelText("Please Wait...");

            // result will be what the label gets set to at the end of this method
            // we set it to Success here to initialize it, knowing that we will only need to change it if an exception actually occurs.
            string result = "Success";

            try {
                // run the long operation
                SomewhatLongRunningOperation(); 
            }
            catch(Exception e)
            {
                // if an exception was caught, we want to update result accordingly
                result = "Error: " + e.Message;
            }

            // Update our label with the result text
            UpdateLabelText(result);
        }

        // This method takes a string and sets our label's text to that value
        // (This could also be turned into a method that updates multiple labels based on variables, rather than one input string affecting one label)
        private void UpdateLabelText(string value) {

            // call our helper funtion on the current control
            // here we use a lambda function (an anonymous method) to create an Action to pass into our method
            // * The lambda function is like a Method that has no name, here our's just updates the label, but it could do anything else we needed
            this.InvokeIfNeeded(() => {

                // set the text of our label to the value
                // (this is where we could set multiple other UI elements (labels, button text, etc) at the same time if we wanted to)
                label.Text = value;
            });
        }

    }