1. <span style='font-family: 宋体; font-size: 10.5pt; mso-bidi-font-size: 11.0pt; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: "Times New Roman"; mso-bidi-theme-font: minor-bidi; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;'><font color="#000000">应用程序配置文件：</font></span>
   
2. <?xml version="1.0" encoding="utf-8" ?>
   
3. <configuration>
   
4.   <connectionStrings>
   
5.     <add name="dbConnStr" connectionString="Data Source=.\SQLEXPRESS; Initial Catalog=MyTest;User ID=sa;Password=123456"/>
   
6.   </connectionStrings>
   
7. </configuration>
   
8. 程序代码：
   
9. <div class="blockcode"><blockquote> private void button1_Click(object sender, RoutedEventArgs e)
   
10.         {
    
11.              string connStr = ConfigurationManager.ConnectionStrings["dbConnStr"].ConnectionString;
    
12.             
    
13.             DataSet dataset = new DataSet();
    
14.             using (SqlConnection conn = new SqlConnection(connStr))
    
15.             {
    
16.                 conn.Open();
    
17.                 MessageBox.Show("连接成功");
    
18.             }
    
19.         }

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产生NullReferenceException异常：未将对象引用设置到对象的实例。找了半天不知错在哪？

1. <span style='font-family: 宋体; font-size: 10.5pt; mso-bidi-font-size: 11.0pt; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: "Times New Roman"; mso-bidi-theme-font: minor-bidi; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;'><font color="#000000">应用程序配置文件：</font></span>
   
2. <?xml version="1.0" encoding="utf-8" ?>
   
3. <configuration>
   
4.   <connectionStrings>
   
5.     <add name="dbConnStr" connectionString="Data Source=.\SQLEXPRESS; Initial Catalog=MyTest;User ID=sa;Password=123456"/>
   
6.   </connectionStrings>
   
7. </configuration>
   
8. 程序代码：
   
9. <div class="blockcode"><blockquote> private void button1_Click(object sender, RoutedEventArgs e)
   
10.         {
    
11.              string connStr = ConfigurationManager.ConnectionStrings["dbConnStr"].ConnectionString;
    
12.             
    
13.             DataSet dataset = new DataSet();
    
14.             using (SqlConnection conn = new SqlConnection(connStr))
    
15.             {
    
16.                 conn.Open();
    
17.                 MessageBox.Show("连接成功");
    
18.             }
    
19.         }

复制代码

产生NullReferenceException异常：未将对象引用设置到对象的实例。找了半天不知错在哪？