错误“对象引用未设置为对象的实例。”为的SqlConnection

Question

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["TropicalConnectionString"].ConnectionString); 

它说

对象引用不设置为一个对象的一个​​实例。

为了检查错误，我给我的app.config，我想知道是否有可能我给初始目录等错误的名称？

这里是我的app.config：

<?xml version="1.0" encoding="utf-8" ?> 
<configuration> 
    <connectionStrings> 
     <add name="TropicalConnectionString" 
      connectionString="Data Source = JIRAN-PC; Initial Catalog = TropicalServer; Integrated Security = True" 
      providerName="System.Data.SqlClient" /> 
     <add name="TropicalServiceWinApp.Properties.Settings.TropicalConnectionString" 
      connectionString="Data Source=JIRAN-PC;Initial Catalog=TropicalServer;Integrated Security=True" 
      providerName="System.Data.SqlClient" /> 
    </connectionStrings> 
    <startup> 
     <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" /> 
    </startup> 
    <system.serviceModel> 
     <bindings> 
      <basicHttpBinding> 
       <binding name="BasicHttpBinding_ITropicalService" /> 
      </basicHttpBinding> 
     </bindings> 
     <client> 
      <endpoint address="http://localhost:5483/TropicalService.svc" 
       binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_ITropicalService" 
       contract="TropicalServiceRef.ITropicalService" name="BasicHttpBinding_ITropicalService" /> 
     </client> 
    </system.serviceModel> 
</configuration> 

Answer 1

试试这个：

1. 在Solution Explorer
2. 在属性窗口中选择app.config文件选择复制到输出目录为始终复制。
3. 现在构建应用程序并重试。