[英]Error shows Object reference not set to an instance of an object?
我是C#和Web服务的新手...当我调试登录代码时,它在浏览器上运行,但是当输入登录按钮时,它显示错误对象引用未设置为具有源错误的对象实例,如下所示:
{
SqlConnection DBConn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ASPNETDBConnectionString"].ConnectionString);
try
{
是否有缺少与数据库连接或连接错误的语法?
您没有名称ASPNETDBConnectionString
的连接字符串,这就是为什么出现此错误的原因。 在使用前请检查是否为null
。
if(System.Configuration.ConfigurationManager.ConnectionStrings["ASPNETDBConnectionString"] != null)
SqlConnection DBConn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ASPNETDBConnectionString"].ConnectionString);
1在System.Configuration上添加引用
2验证您的App.Config或Web.Config中是否存在ASPNETDBConnectionString字符串连接
注意:您的config文件中必须包含ASPNETDBConnectionString这一节
<connectionStrings>
<add
name="ASPNETDBConnectionString"
connectionString="Data Source=serverName;Initial
Catalog=...;Persist Security Info=True;User
ID=userName;Password=password"
providerName="System.Data.SqlClient"
/>
</connectionStrings>
firstly add connection string to web config file as follows:
***<configuration>
<system.web>
<compilation debug="true" targetFramework="4.0"/>
</system.web>
<connectionStrings>
<add name="key" connectionString="....." providerName="System.Data.SqlClient"/>
</connectionStrings>
</configuration>***
then add namespace to .cs page
> using System.Configuration;
then create a connection string on page as:-
***cn = new SqlConnection();
cn.ConnectionString = ConfigurationManager.ConnectionStrings["key"].ConnectionString;***
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