我正在尝试使用app.config连接数据库，问题是它在框架中工作正常（visual studio 2012）但是当我创建设置时，运行它后通过快速启动它通过连接字符串的null异常，这是我的连接和例外。 db文件放在D：\ Account \ Account \ bin \ x86 \ Debug中。通过连接字符串它工作正常，但我想使用app.config
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
</configSections>
<connectionStrings>
<add name="myconnection" connectionString="Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Account.accdb"
providerName="System.Data.OleDb" />
</connectionStrings>
</configuration>
myconnection = New OleDbConnection
Dim ConnectionString As String = ConfigurationManager.ConnectionStrings("myconnection").ConnectionString
'Dim ConnectionString As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Account.accdb"
myconnection.ConnectionString = ConnectionString
myconnection.Open()
'Here is the null exception
See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.
************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
at Account.Common.ConnectDb()
at Account.FrmLogin.FrmLogin_Load(Object sender, EventArgs e)
at System.EventHandler.Invoke(Object sender, EventArgs e)
at System.Windows.Forms.Form.OnLoad(EventArgs e)
at System.Windows.Forms.Form.OnCreateControl()
at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
at System.Windows.Forms.Control.CreateControl()
at System.Windows.Forms.Control.WmShowWindow(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Form.WmShowWindow(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
************** Loaded Assemblies **************
mscorlib
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.18010 built by: FX45RTMGDR
CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll
----------------------------------------
Account
Assembly Version: 1.0.0.0
Win32 Version: 1.0.0.0
CodeBase: file:///C:/Program%20Files/Manoj/My%20Product%20Name/Account.exe
----------------------------------------
Microsoft.VisualBasic
Assembly Version: 10.0.0.0
Win32 Version: 11.0.50709.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Microsoft.VisualBasic/v4.0_10.0.0.0__b03f5f7f11d50a3a/Microsoft.VisualBasic.dll
----------------------------------------
System
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.18016 built by: FX45RTMGDR
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll
----------------------------------------
System.Core
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll
----------------------------------------
System.Windows.Forms
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
----------------------------------------
System.Drawing
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
----------------------------------------
System.Configuration
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Configuration/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll
----------------------------------------
System.Xml
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Xml/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.dll
----------------------------------------
System.Runtime.Remoting
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Runtime.Remoting/v4.0_4.0.0.0__b77a5c561934e089/System.Runtime.Remoting.dll
----------------------------------------
System.Data
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.17929 built by: FX45RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_32/System.Data/v4.0_4.0.0.0__b77a5c561934e089/System.Data.dll
----------------------------------------
************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.
For example:
<configuration>
<system.windows.forms jitDebugging="true" />
</configuration>
When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.