Cannot open database "GADatabase". The login failed. HELP!

Question

Cannot open database "GADatabase" requested by the login. The login failed. HELP!

Hey, i are in the makings of a program C# at my school, and i have a Databae in SQL Server management studios called GADatabase

I have my database class like this

public class Database
{
    private static SqlCommand ObjCmd;
    static string SqlConn = "Data Source=localhost\\SQLEXPRESS;Initial Catalog=GADatabase;Integrated Security=SSPI;";
    private static SqlConnection ObjConn = new SqlConnection(SqlConn);

    public Database()
    {
    }

    public void AddStudent(Student Student)
    {
        ObjConn.Open();
        ObjCmd = ObjConn.CreateCommand();
        ObjCmd.CommandType = System.Data.CommandType.Text;
        int i = 0;
        try
        {
            ObjCmd.CommandText = string.Concat(Student.InsertSqlQuery);
            i = ObjCmd.ExecuteNonQuery();

        }
        catch{ }

        ObjConn.Close();
    }
}

  

but if i call the AddStudent and try to acces the ObjConn.Open(); it just returns and gives me the error "Cannot open database "GADatabase" requested by the login. The login failed."

Please if anyone can help me with this error :)
and feel free to ask for more information if that is what u need to help me with my problem