Question

我想在

中初始化ConnectionManager

 public ShowVoc()
            {
                InitializeComponent();

                connectionString = ConfigurationManager.ConnectionStrings["WindowsFormsApplication1.Properties.Settings.splaceConnectionString;"].ConnectionString;
            }

但无论何时我运行它都会给我＆＃39; System.NullReferenceException＆＃39;

这是应用配置代码

<?xml version="1.0" encoding="utf-8" ?>
    <configuration>
        <configSections>
        </configSections>
        <connectionStrings>
            <add name="WindowsFormsApplication1.Properties.Settings.splaceConnectionString"
                connectionString="Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\splace.mdf;Integrated Security=True"
                providerName="System.Data.SqlClient" />
            <add name="WindowsFormsApplication1.Properties.Settings.VocConnectionString"
                connectionString="Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Voc.mdf;Integrated Security=True"
                providerName="System.Data.SqlClient" />
        </connectionStrings>
        <startup> 
            <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
        </startup>
    </configuration>

这是例外细节

System.NullReferenceException未处理HResult = -2147467261
Message =对象引用未设置为对象的实例 Source = WindowsFormsApplication1 StackTrace：在C：\ Users \ user \ Documents \ Visual Studio中的WindowsFormsApplication1.ShowVoc..ctor（） 2015年\项目\ WindowsFormsApplication1 \ WindowsFormsApplication1 \ ShowVoc.cs：行 24 at WindowsFormsApplication1.main.voc_Click_1（Object sender，EventArgs e）在C：\ Users \ user \ Documents \ Visual Studio中 2015年\项目\ WindowsFormsApplication1 \ WindowsFormsApplication1 \ main.cs：行 53 在System.Windows.Forms.Control.OnClick（EventArgs e）在System.Windows.Forms.Button.OnClick（EventArgs e）在System.Windows.Forms.Button.OnMouseUp（MouseEventArgs mevent）在System.Windows.Forms.Control.WmMouseUp（消息＆amp; m，MouseButtons按钮，Int32点击）在System.Windows.Forms.Control.WndProc（消息＆amp; m）在System.Windows.Forms.ButtonBase.WndProc（消息＆amp; m）在System.Windows.Forms.Button.WndProc（消息＆amp; m）在System.Windows.Forms.Control.ControlNativeWindow.OnMessage（Message＆amp; m）在System.Windows.Forms.Control.ControlNativeWindow.WndProc（Message＆amp; m）在System.Windows.Forms.NativeWindow.DebuggableCallback（IntPtr hWnd，Int32 msg，IntPtr wparam，IntPtr lparam）在System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW（MSG＆amp; msg）在System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop（IntPtr） dwComponentID，Int32原因，Int32 pvLoopData）在System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner（Int32）原因，ApplicationContext上下文）在System.Windows.Forms.Application.ThreadContext.RunMessageLoop（Int32）原因，ApplicationContext上下文）在System.Windows.Forms.Application.Run（Form mainForm）在C：\ Users \ user \ Documents \ Visual Studio中的WindowsFormsApplication1.Program.Main（） 2015年\项目\ WindowsFormsApplication1 \ WindowsFormsApplication1 \的Program.cs：行 19 在System.AppDomain._nExecuteAssembly（RuntimeAssembly程序集，String [] args）在System.AppDomain.nExecuteAssembly（RuntimeAssembly程序集，String [] args）在System.Runtime.Hosting.ManifestRunner.Run（Boolean checkAptModel）在System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly（）在System.Runtime.Hosting.ApplicationActivator.CreateInstance（ActivationContext activationContext，String [] activationCustomData）在System.Runtime.Hosting.ApplicationActivator.CreateInstance（ActivationContext activationContext）在System.Activator.CreateInstance（ActivationContext activationContext）在Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone（）在System.Threading.ThreadHelper.ThreadStart_Context（对象状态）在System.Threading.ExecutionContext.RunInternal（ExecutionContext executionContext，ContextCallback回调，对象状态，布尔值 preserveSyncCtx） at System.Threading.ExecutionContext.Run（ExecutionContext executionContext，ContextCallback callback，Object state，Boolean preserveSyncCtx）在System.Threading.ExecutionContext.Run（ExecutionContext executionContext，ContextCallback回调，对象状态）在System.Threading.ThreadHelper.ThreadStart（）InnerException：

PS：我已经添加了对System.configration的引用

Answer 1

将来，在提出新问题之前，请先使用Google和SO自己的搜索引擎搜索您的问题。 System.NullReferenceException在整个地方都有详细的解释。要解决您的问题，请转到

public ShowVoc()
        { string connectionString="";
            InitializeComponent();

            connectionString = ConfigurationManager.ConnectionStrings["WindowsFormsApplication1.Properties.Settings.splaceConnectionString;"].ConnectionString;
        }

Answer 2

在你的连接字符串中，我看到一个不需要的;在末尾。我想你不需要那个。正确的版本应该是：

connectionString = ConfigurationManager
    .ConnectionStrings["WindowsFormsApplication1.Properties.Settings.splaceConnectionString"]
    .ConnectionString;

Answer 3

难道只是连接字符串中的拼写错误？我看到你在结尾添加了一个分号，这在XML中不存在。删除它应该没问题。

＆＃39; System.NullReferenceException＆＃39;初始化ConnectionManager

3 个答案: