Can't connect to SQL Server: "Login failed for user "."

Question

I'm new with .NET and have hit a brick wall. I'm writing code in C# to access a Microsoft SQL Server 2008. This is the code from my app.config file

<configuration>
  <appSettings>
    <add key="provider" value="System.Data.SqlClient" />
  </appSettings>
  <connectionStrings>
      <add name ="AutoLotSqlProvider"  connectionString =
           "Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Program Files\Microsoft SQL  Server\MSSQL10_50.SQLEXPRESS\MSSQL\DATA\AutoLot.mdf"/>   
     <add name ="AutoLotOleDbProvider"  connectionString =
     "Provider=SQLOLEDB;Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Program Files\Microsoft SQL Server\MSSQL10_50.SQLEXPRESS\MSSQL\DATA\AutoLot.mdf"/>
     </connectionStrings>
</configuration>

When I debug the C# program I'm getting this error message:

System.Data.SqlClient.SqlException { Login failed for user "." }

I cannot find a user name in the database

This is my program code:

public class Program
{
    static void Main(string[] args)
    {
        // Get Connection string/provider from *.config.
        Console.WriteLine("***** Fun with Data Provider Factories *****\n");
        string dp = ConfigurationManager.AppSettings["provider"];
        string cnStr = ConfigurationManager.ConnectionStrings["AutoLotSqlProvider"].ConnectionString;

        // Get the factory provider.
        DbProviderFactory df = DbProviderFactories.GetFactory(dp);

        // Now make connection object.
        using (DbConnection cn = df.CreateConnection())
        {
            Console.WriteLine("Your connection object is a: {0}", cn.GetType().Name);
            cn.ConnectionString = cnStr;
            cn.Open();
            if (cn is SqlConnection)
            {
                // Print out which version of SQL Server is used.
                Console.WriteLine(((SqlConnection)cn).ServerVersion);
            }

            // Make command object.
            DbCommand cmd = df.CreateCommand();
            Console.WriteLine("Your command object is a: {0}", cmd.GetType().Name);
            cmd.Connection = cn;
            cmd.CommandText = "Select * From Inventory";

            // Print out data with data reader.              
            using (DbDataReader dr = cmd.ExecuteReader())
            {
                Console.WriteLine("Your data reader object is a: {0}", dr.GetType().Name);

                Console.WriteLine("\n***** Current Inventory *****");
                while (dr.Read())
                    Console.WriteLine("-> Car #{0} is a {1}.",
                      dr["CarID"], dr["Make"].ToString());
            }
        }
    }
}

Solution 1

In your connection string, you haven't specified whether you want Windows Authentication or SQL Authentication. For SQL auth it should be (obviously replace x and y with your username and password):

<add name ="AutoLotSqlProvider" connectionString = 
 "Data Source=.\SQLEXPRESS;User ID=x;Password=y;AttachDbFilename=C:\...\AutoLot.mdf"/>

For Windows auth it should be:

<add name ="AutoLotSqlProvider"  connectionString =
 "Data Source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDbFilename=C:\...\AutoLot.mdf"/>

Solution 2

Your connection string is missing an authentication scheme. You need to either pass a username/password or use integrated security when creating a connection.

Solution 3

You need to specify a Username and Password to login to Sql database.

For a list of connection strings check ConnectionStrings

OLEDB connection string for sql 2008 is Provider=SQLNCLI10;Server=myServerAddress;Database=myDataBase;Uid=myUsername; Pwd=myPassword;