User Instance Error

 Hello.
I am trying to connect to a MsSQL Server database and i keep getting this error.

Instance Failure

Description: An
unhandled exception occurred during the execution of the current web
request. Please review the stack trace for more information about the
error and where it originated in the code.


Exception Details: System.InvalidOperationException: Instance failure.



Source Error:







Line 23: SqlConnection connection = new SqlConnection();
Line 24: connection.ConnectionString = str;
Line 25: connection.Open(); [InvalidOperationException: Instance failure.]
System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, SqlConnection owningObject) +737932
System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +114
System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +282
System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +181
System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +173
System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +357
System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +30
System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +424
System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +66
System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +494
System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +82
System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +105
System.Data.SqlClient.SqlConnection.Open() +111
sign.enter_Click(Object sender, ImageClickEventArgs e) in e:WorkLicentasign.aspx.cs:25
System.Web.UI.WebControls.ImageButton.OnClick(ImageClickEventArgs e) +86
System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument) +115
System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1746  Here is my code. I am trying to read my connection string from webconfig. I tried to put the connection string directly in the code and it works fine, but i want to get it from the webconfig xml. string str = System.Configuration.ConfigurationManager.ConnectionStrings["messengerConnectionString"].ConnectionString;
SqlConnection connection = new SqlConnection();
connection.ConnectionString = str;
connection.Open();
if (connection != null)
{
connection.Close();
connection.Dispose();
}   <connectionStrings>
<add name="messengerConnectionString" connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=messenger;User ID=muncitoru;Password=alcatel"
providerName="System.Data.SqlClient" />
</connectionStrings>
  Thanks in advance!