检查选中哪个单选按钮的方法始终返回null [英] Method to check which Radio button is checked always returns null

问题描述

所以我在Form类中有一个方法来检查GroupBox中的哪个RadioButtons被选中，从而返回一个字符串。



然后我创建一个实例在这样的另一个类中形成

So I have a method in my Form class to check which RadioButtons in a GroupBox are selected, and thus return a string.

I then create an instance of Form in another class like this

Form1 form = new Form1();

然后我使用该对象从表单类调用我的方法

I then use that object to call my method from the form class

form.whatChecked();

这个表单类中的方法

This is my method in the form class

public String whatChecked()
        {
            if (a1.Checked)
            {
                return "a1";
            }
            else if (a2.Checked)
            {
                return "a2";
            }
            else if (a2.Checked)
            {
                return "a3";
            }
            else if (a2.Checked)
            {
                return "a4";
            }
            else if (a2.Checked)
            {
                return "a5";
            }
            else if (a2.Checked)
            {
                return "a6";
            }
            else
            {
                return null;
            }
        }

我在另一堂课上检查了一下，我发现它总是返回else值（在本例中为Null）。我已经测试过确保让else返回一个String，并确实返回，即使检查了a1或a2。

I've made a check in the other class, and I see that it always returns the "else" value (In this case, Null). I've tested to make sure by having the else return a String, and it does indeed return, even though a1 or a2 are checked.

推荐答案

你似乎检查在大多数情况下，相同的单选按钮。代码应该是这样的：

You seem to check the same radio button in most of the cases. Should the code look like:

public String whatChecked()
        {
            if (a1.Checked)
            {
                return "a1";
            }
            else if (a2.Checked)
            {
                return "a2";
            }
            else if (a3.Checked)
            {
                return "a3";
            }
            else if (a4.Checked)
            {
                return "a4";
            }
            else if (a5.Checked)
            {
                return "a5";
            }
            else if (a6.Checked)
            {
                return "a6";
            }
            else
            {
                return null;
            }
        }

增加：

ADDED:

private void radioButtons_CheckedChanged(Object sender, EventArgs e)
{
   if (a1.Checked))
   {
      // here execute the code what needs to be done when a1 is selected
      // in the same event handler also add code for other radio buttons since 
      // this event handler will be used for all radio buttons
   }
}

在Form_Load事件或构造函数中，连接所有复选框以使用相同的事件处理程序

And in the Form_Load event or constructor, wire all the check boxes to use the same event handler

this.a1.CheckedChanged += new System.EventHandler(this.radioButtons_CheckedChanged);
this.a2.CheckedChanged += new System.EventHandler(this.radioButtons_CheckedChanged);
this.a3.CheckedChanged += new System.EventHandler(this.radioButtons_CheckedChanged);
this.a4.CheckedChanged += new System.EventHandler(this.radioButtons_CheckedChanged);
...

这段代码我从Mika发布的解决方案中删除了一点点（我希望你能原谅我Mika ）。

This code I have taken from the posted Solution from Mika to change it a little bit (I hope you will forgive me Mika).

private void radioButtons_CheckedChanged(Object sender, EventArgs e)
{
   RadioButton mySender = sender ;
   if (mySender.Checked) && (mySender.Name="A1")
   {
      // here execute the code what needs to be done when a1 is selected
      // in the same event handler also add code for other radio buttons since 
      // this event handler will be used for all radio buttons
   }
}

这也可能如下所示：

this could also look like this :

private void radioButtons_CheckedChanged(Object sender, EventArgs e)
{
	if (! object.ReferenceEquals(Sender.gettype, typeof(radiobutton))) return;  // if incomming object is not radiobutton


radiobutton mySender = Sender;
if (mySender.Checked) 
   {

   switch (mySender.name) {
	case "a1":
                // do the Action here
		break;
	case "a2":
                // do the Action here
		break;
      }
   }
}

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