I am trying to get a value of output parameter which I used in my stored procedure, but I am not getting it. I've been trying hard but could not figure it out. The program is not throwing any error, but in the end, the value of _clientCode is null (Refer screenshot):

I need your support, please help me to find out where I need to change.

public string getData5(string icuser)
{
    string _clientCode;

    SqlDataReader dataReader;
            
    SqlConnection conn = new SqlConnection();
    conn.ConnectionString = "Server=xxx-dbprod;DataBase=TCS;Integrated Security=True;";
                // conn.ConnectionString = "Data Source = tcr-dbprod; Initial Catalog = TCS; Integrated Security = True;";
                //conn.ConnectionString = ConfigurationManager.ConnectionStrings["CS"].ConnectionString;

    SqlCommand command = new SqlCommand();
    command.Connection = conn;
    command.CommandType = CommandType.StoredProcedure;
    command.CommandText = "[dbo].[spTCRGetClientCode]";

    command.Parameters.AddWithValue("@icUserID", icuser);
    command.Parameters.Add(new SqlParameter("@clientCode", SqlDbType.NVarChar, 300));
    command.Parameters["@clientCode"].Direction = ParameterDirection.Output;
    
    try
    {
        conn.Open();

        int i = command.ExecuteNonQuery();
        dataReader = command.ExecuteReader();

        _clientCode = Convert.ToString(command.Parameters["@clientCode"].Value);
        conn.Close();

        return _clientCode;
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
        return null;
        //conn.Close();
        //DbConnection.Dispose();
    }
}

I explained in my question detail and attached the screenshot for your help.