C# + sql

Question

hello, i want to fill a grid with this code, without the WHERE condition my code works fine, but when i try to filter on username, it fails.

I made a Session Username and this is my code:

public ICollection<Aanvraag> GetAllAanvragen()

{

List<Aanvraag> result = new List<Aanvraag>();

using (SqlConnection connection = new SqlConnection(_connectionString))

using (SqlCommand command = new SqlCommand())

{

command.CommandText = "SELECT VID, State, Begindatum, Einddatum, WorkflowInstanceID, Opmerking, Type, Username FROM tblVerlofaanvraag WHERE Username = 'Session[username].ToString()'";

connection.Open();

command.Connection = connection;

using (SqlDataReader reader = command.ExecuteReader())

{

while (reader.Read())

{

result.Add(Aanvraag.CreateFromDataReader(reader));

}

}

}

return result;

}