Line 37:             dt = new DataTable();
Line 38:             string chkUser = "Select * FROM [tbl_User] where Email='" + UserName + "' AND Password='" + Password + "'";
Line 39:             dt = dbClass.ConnectDataBaseReturnDT(chkUser);
Line 40:             if (dt.Rows.Count > 0)
Line 41:             {

[SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)]
   System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling, SqlAuthenticationProviderManager sqlAuthProviderManager) +947
   System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) +342
   System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions) +38
   System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) +726
   System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) +91
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) +438
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) +79
   System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) +201
   System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +156
   System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +22
   System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) +92
   System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry) +219
   System.Data.SqlClient.SqlConnection.Open() +101
   System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +121
   System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior) +162
   System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) +111
   R_OnLine_File_Management_System.DataBaseClass.ConnectDataBaseReturnDT(String Query) in c:\Users\Rahul\Documents\Visual Studio 2012\Projects\R-OnLine File Management System\R-OnLine File Management System\DataBaseClass.cs:56
   R_OnLine_File_Management_System.Login.UserAuthenticate(String UserName, String Password) in c:\inetpub\wwwroot\Document Mgmt System\R-OnLine File Management System\R-OnLine File Management System\Login.aspx.cs:39
   R_OnLine_File_Management_System.Login.OnAuthenticate(Object sender, AuthenticateEventArgs e) in c:\inetpub\wwwroot\Document Mgmt System\R-OnLine File Management System\R-OnLine File Management System\Login.aspx.cs:26
   System.Web.UI.WebControls.Login.OnAuthenticate(AuthenticateEventArgs e) +9794378
   System.Web.UI.WebControls.Login.AttemptLogin() +122
   System.Web.UI.WebControls.Login.OnBubbleEvent(Object source, EventArgs e) +79
   System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37
   System.Web.UI.WebControls.Button.OnCommand(CommandEventArgs e) +120
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +272
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +12
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +15
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +35
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1696