不检查单选按钮列表中的项目 [英] Not checking an item in a Radio Button List

问题描述

亲爱的所有人，

我正在为测验应用程序使用单选按钮列表.

我想实现用户可以不作任何选择的功能.

也就是说，我没有使用强制验证.

但这在我检查问题是对还是错并计算分数时失败.

它说空引用异常.

以下是代码段.

Dear All,

I am using a Radio Button List for my quiz application.

I want to implement the functionality that the user can leave an answer unchecked.

That is, I am not using the Mandatory Validation.

But this fails when I am checking whether the question is right or wrong and while calculating score.

It says Null Reference Exception.

Below is the code snippet.

protected void Button1_Click(object sender, EventArgs e)
    {
        intTotalQuestion = (int)ViewState["TotalQuestion"];
        intQuestionNo = (int)ViewState["QuestionNo"];
        intScore = (int)ViewState["Score"];
        Answers = (ArrayList)ViewState["AnswerHistory"];
        
         if (RadioButtonList1.SelectedItem.Value == ViewState["CorrectAnswer"].ToString())
        {
            intScore += 10;
        }
        else
        {
            intScore = intScore - 1;
        }
        if (intQuestionNo == intTotalQuestion)
        {
            Response.Write("Your Score is " + intScore.ToString() + " Points");
            Response.Write("\n\n");
            Response.Write("Quiz over");
        }
        else
        {
            intQuestionNo = intQuestionNo + 1;
            ShowQuestion(intQuestionNo);
        }
    }

在此获取错误:

Getting the error here :

if (RadioButtonList1.SelectedItem.Value == ViewState["CorrectAnswer"].ToString())

对你们来说，这可能是一个简单的问题...但是当我是初学者时，我正面临着这个问题...:confused :: confused :: confused :: confused :: confused :: confused:

请协助...

谢谢
MK

This might as a simple problem to you guys...But I am facing this problem as I am a beginner...:confused::confused::confused::confused::confused::confused:

Kindly assist...

Thanks
MK

推荐答案

如果尚未选择项目，则SelectedItem为null.尝试以下方法:

If they haven''t selected an item, then SelectedItem is null. Try this instead:

if (RadioButtonList1.SelectedItem != null && 
    RadioButtonList1.SelectedItem.Value == ViewState["CorrectAnswer"].ToString())

&&运算符将对if语句的第一部分求值，如果它== null，它将停止撤消操作，并且您不会收到错误.

The && operator will evaluate the first part of the if statement and if it == null, it will stop evaulating and you won''t get the error.

这篇关于不检查单选按钮列表中的项目的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！