c# - ADO.NET - The Size property has an invalid size of 0

Question

I'm trying to get output value from DB via ADO.NET. There's a client code:

    using (var connection = new SqlConnection(ConnectionString))
    {
        connection.Open();
        SqlCommand command = new SqlCommand("pDoSomethingParamsRes", connection);
        command.CommandType = CommandType.StoredProcedure;
        command.Parameters.Add("@i", 1);
        var outParam = new SqlParameter("@out", SqlDbType.VarChar);
        outParam.Direction = ParameterDirection.Output;
        command.Parameters.Add(outParam);
        command.ExecuteNonQuery();
        Console.WriteLine(command.Parameters["@out"].Value.ToString());
    }

When I run this I get the following exception:

the Size property has an invalid size of 0

According to manual SqlParameter.Size Property I might omit size. Why do I get this exception?

How to make it work without passing size?

Answer 1

VarChar and NVarChar are variable width character fields (thus var+char). You have to set the length, otherwise the default is zero.