高分问一道题,请大家都来看一下

 图在左边的,代码如下,     里面的正确选项则C都选中C的时候会弹出"成功",但是你马上去点A或者B或者C的时候也会弹出成功,请问这个怎么解决呀
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace WindowsApplication2
{
    public partial class Form1 : Form
    {
        private SqlConnection tion;
        private SqlCommand and;
        private string sql;
        private SqlDataReader rd;
        private int sum = 0;
        public Form1()
        {
            InitializeComponent();
        }

        private void radioButton1_CheckedChanged(object sender, EventArgs e)
        {
            
             //tion = new SqlConnection("server=.;database=ddt;uid=sa;pwd=");
             sql = "select * from name where name='"+this.radioButton1.Text+"'";

             try
             {
                 tion.Open();
                 and = new SqlCommand(sql, tion);
                 rd = and.ExecuteReader();
                 if (rd.Read())
                 {
                     MessageBox.Show("成功");
                     sum = sum + 25;
                 }
             }
             catch (SqlException ex)
             {
                 MessageBox.Show(ex.Message);
             }
             finally {
                 tion.Close();
                 rd.Close();
                 and.Dispose();
             }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            tion = new SqlConnection("server=.;database=ddt;uid=sa;pwd=");
            //tion.Open();
        }

        private void radioButton2_CheckedChanged(object sender, EventArgs e)
        {
            //tion = new SqlConnection("server=.;database=ddt;uid=sa;pwd=");
            sql = "select * from name where name='" + this.radioButton2.Text + "'";

            try
            {
                tion.Open();
                and = new SqlCommand(sql, tion);
                rd = and.ExecuteReader();
                if (rd.Read())
                {
                    MessageBox.Show("成功");
                    sum = sum + 25;
                }
            }
            catch (SqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                tion.Close();
                rd.Dispose();
                and.Dispose();
            }
        }

        private void radioButton3_CheckedChanged(object sender, EventArgs e)
        {
            //tion = new SqlConnection("server=.;database=ddt;uid=sa;pwd=");
            sql = "select * from name where name='" + this.radioButton3.Text + "'";

            try
            {
                tion.Open();
                and = new SqlCommand(sql, tion);
                rd = and.ExecuteReader();
                if (rd.Read())
                {
                    MessageBox.Show("成功");
                    sum = sum + 25;
                }
            }
            catch (SqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                tion.Close();
            }
        }

        private void radioButton4_CheckedChanged(object sender, EventArgs e)
        {
            
            //tion = new SqlConnection("server=.;database=ddt;uid=sa;pwd=");
            sql = "select * from name where name='" + this.radioButton4.Text + "'";

            try
            {
                tion.Open();
                and = new SqlCommand(sql, tion);
                rd = and.ExecuteReader();
                if (rd.Read())
                {
                    MessageBox.Show("成功");
                    sum = sum + 25;
                }
            }
            catch (SqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                tion.Close();
                rd.Close();
                and.Dispose();
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.label1.Text = "你的成绩是" + sum + "分";
        }
    }
} --------------------编程问答-------------------- 是不是SUM要清一下零 --------------------编程问答-------------------- 不需要,不管SUM的事 --------------------编程问答-------------------- 什么意思？代码中有四句  

MessageBox.Show("成功"); 

--------------------编程问答-------------------- this.radioButton4.Text 
换成 radioButton.SelectedItems.Text呢 --------------------编程问答-------------------- radioButton是不包含SelectedItems的定义的 --------------------编程问答-------------------- 楼主你的四段代码可以用下面这一段来代替 

      private void radioButton1_CheckedChanged(object sender, EventArgs e) 
        { 
            
            //tion = new SqlConnection("server=.;database=ddt;uid=sa;pwd="); 
            sql = "select * from name where name='"+ (sender as RadioButton).Text+"'"; 

            try 
            { 
                tion.Open(); 
                and = new SqlCommand(sql, tion); 
                rd = and.ExecuteReader(); 
                if (rd.Read()) 
                { 
                    MessageBox.Show("成功"); 
                    sum = sum + 25; 
                } 
            } 
            catch (SqlException ex) 
            { 
                MessageBox.Show(ex.Message); 
            } 
            finally { 
                tion.Close(); 
                rd.Close(); 
                and.Dispose(); 
            } 
        } 

补充：.NET技术 ,  C#