c# - Get output parameter value of a stored procedure using EF Core?

Question

I am using Asp.net core and EF core in my application. Basically I want to get multiple result set from a single stored procedure. Tried to search it for last 2 days no such luck. Tried to figure out a work around to resolve it..

This is my stored procedure:

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

ALTER PROCEDURE [dbo].[usp_CustomerAll_sel]
    @SomeOutput int OUT
AS
BEGIN
    SET NOCOUNT ON;

    SELECT * 
    FROM [dbo].[Customer]

    SELECT @SomeOutput = @@rowcount + 25 --This number 25 is a variable from a complex query but always an integer
END

I have 2 records in that table, so basically it should return a table of customer type and output parameter should return 27..

Now from my .net code what I have tried so far

[HttpGet]
public async Task<Tuple<IEnumerable<Customer>, int>> GetAllCustomer()
{
    var votesParam = new SqlParameter
            {
                ParameterName = "SomeOutput",
                Value = -1,
                Direction = ParameterDirection.Output
            };

    var y = await _customerContext.Customers.FromSql("usp_CustomerAll_sel @SomeOutput out", votesParam).ToArrayAsync();

    return new Tuple<IEnumerable<Customer>, int>(y, (int)votesParam.Value);
}

Above one returning me the list but I am not getting the value of output parameter from DB .(int)votesParam.Value is showing null

Now if I use ExecuteNonQueryAsync, then I am getting the output parameter but not the actual data

private async Task ExecuteStoredProc()
{
    DbCommand cmd = _customerContext.Database.GetDbConnection().CreateCommand();

    cmd.CommandText = "dbo.usp_CustomerAll_sel";
    cmd.CommandType = CommandType.StoredProcedure;

    cmd.Parameters.Add(new SqlParameter("@SomeOutput", SqlDbType.BigInt) { Direction = ParameterDirection.Output, Value = -1 });

    if (cmd.Connection.State != ConnectionState.Open)
    {
        cmd.Connection.Open();
    }

    await cmd.ExecuteNonQueryAsync();

    long SomeOutput = (long)cmd.Parameters["@SomeOutput"].Value;
}

Is there any way to get both result set and the output parameter and return as a tuple?

When I just put the hard coded value then it's looks like

[HttpGet]
public async Task<Tuple<IEnumerable<Customer>, int>> GetAllCustomer()
{
    var votesParam = new SqlParameter
    {
        ParameterName = "SomeOutput",
        Value = -1,
        Direction = ParameterDirection.Output
    };

    var y = await _customerContext.Customers.FromSql("usp_CustomerAll_sel @SomeOutput out", votesParam).ToArrayAsync();
    return new Tuple<IEnumerable<Customer>, int>(y, **25**);
}

And result like

{"item1":[{"customerId":1,"customerName":"Cus1"},{"customerId":2,"customerName":"Cus2"}],"item2":27}

Basically this is what I am looking for... Any help?

Answer 1

In EF Core you can't return ad-hoc types from raw SQL queries yet (they are working on this), so you will need a workaround for this issue. Add this class to your project:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Internal;
using Microsoft.EntityFrameworkCore.Storage;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Collections.Generic;
using System.Data.Common;
using System.Linq;
using System.Reflection;
using System.Threading;
using System.Threading.Tasks;

namespace Microsoft.EntityFrameworkCore
{

    public static class RDFacadeExtensions
    {
        public static RelationalDataReader ExecuteSqlQuery(this DatabaseFacade databaseFacade, string sql, params object[] parameters)
        {
            var concurrencyDetector = databaseFacade.GetService<IConcurrencyDetector>();

            using (concurrencyDetector.EnterCriticalSection())
            {
                var rawSqlCommand = databaseFacade
                    .GetService<IRawSqlCommandBuilder>()
                    .Build(sql, parameters);

                return rawSqlCommand
                    .RelationalCommand
                    .ExecuteReader(
                        databaseFacade.GetService<IRelationalConnection>(),
                        parameterValues: rawSqlCommand.ParameterValues);
            }
        }
    }
}

Then you can call the method below and get the OUTPUT from you SP, here's a sample:

            var _sMsg = new SqlParameter("sMsg", "")
            {
                Direction = ParameterDirection.Output,
                DbType = DbType.String,
                Size = 500
            };

            var sql = "exec sp_foo @sUserId, @sMsg OUTPUT";

            using (var dr = _ctx.Database.ExecuteSqlQuery(sql, _sUserID, _sMsg))
            {
                //here you can retrive your table
                while (dr.DbDataReader.Read())
                {
                    var bar = dr.DbDataReader[0].ToString();
                }

                //here is your OUTPUT
                return _sMsg.Value.ToString();
            }