从C＃连接到SQL Server Express

Question

I'm trying to connect to a SQL Server database from C#, but keep get thrown by an exception:

System.Data.SqlClient.SqlException when trying to open()` the connection.

I have created a simple web form, with two text boxes: usernameTextBox, and passwordTextBox, and a 'sign in' button.

For now, just for testing purposes, what I'm trying to do is to insert values into a users table, when the sign in button is clicked, so this is what I have so far:

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _default : System.Web.UI.Page
{
    protected void signInButton_Click(object sender, EventArgs e)
    {
        string connection_str="Data Source=.\\SQLEXPRESS;"+
        "AttachDbFilename=|DataDirectory|\\project.mdf;"+
        "Integrated Security=True;"+
        "User Instance=True";

        SqlConnection connection = new SqlConnection(connection_str);
        connection.Open();

        SqlCommand command = new SqlCommand();
        command.Connection = connection;
        command.CommandText="INSERT INTO users VALUES ('"+userNameTextBox.Text+"','"+passwordTextBox.Text+"');";
        command.ExecuteNonQuery();
        connection.Close();
    }
}

As stated above, this fails at connection.Open(); .

The project.mdf file is located at the VS Project folder, inside the 'App_Data' folder.

Does anyone have an idea about what can cause the Open() to fail?

I can also provide the 'exception info', if it is needed.

Thanks.

BTW, When should the connection be established? at the 'sign-in-button handler', or in the 'Page_Load' handler?

EDIT

System.Data.SqlClient.SqlException was unhandled by user code
  HResult=-2146232060
  Message=Cannot open user default database. Login failed.
Login failed for user 'J***-PC\J***'.
  Source=.Net SqlClient Data Provider
  ErrorCode=-2146232060
  Class=11
  LineNumber=65536
  Number=4064
  Procedure=""
  Server=\\.\pipe\8EDE82F8-E3AA-40\tsql\query
  State=1
  StackTrace:
       at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
       at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
       at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
       at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
       at System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK)
       at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover)
       at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout)
       at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
       at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData)
       at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
       at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
       at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
       at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
       at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
       at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
       at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
       at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
       at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
       at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
       at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
       at System.Data.SqlClient.SqlConnection.Open()
       at _default.signInButton_Click(Object sender, EventArgs e) in c:\Users\J***\Documents\Visual Studio 2012\Projects\db5774\default.aspx.cs:line 23
       at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
       at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
  InnerException: 

Answer 1

So the exception says:

Message=Cannot open user default database. Login failed. Login failed for user 'J***-PC\\J***'.

That would mean the user has no access to the default database, usually master .

Alter the user so it can access the default database, or better, point the default to another database.

Use this sql for that:

alter login [username] with default_database = database_that_user_can_access

Or change the connection string by adding this:

Database=database_that_user_can_access

Answer 2

尝试这个：

  AttachDbFilename=~\..\ProjectName\App_Data\project.mdf