The required column 'Col0' was not present in the results of a 'FromSql' operation.

Executing a stored procedure resulted in the following exception: System.InvalidOperationException: The required column ‘Col0’ was not present in the results of a ‘FromSql’ operation.

The stored procedure in question returns a result with no column name (dbo.sp_describe_first_result_set shows null for name). It seems the reverse engineering is automatically adding in “Col{index}” to the result.

I was expecting an empty partial result class.

PS: it is an easy fix for the developer to provide a column name in the stored procedure but unfortunately this database is read-only (developer lacking schema change permission).

Steps to reproduce

Create a stored procedure like so:

CREATE PROCEDURE dbo.Test()
AS
BEGIN 
	DECLARE @Id INT = 0
	SELECT @Id
END

Reverse engineer the above-stored procedure and notice the generated result class to have a property called Col0. When executing the stored procedure the exception is thrown.

Further technical details

EF Core version in use: 5

EF Core Power Tools version: 2.5.866

Database engine: SQL Server 2019

Visual Studio version: Visual Studio 2019 16.11.8

[ducman]

The example sproc in the 1st post does SELECT @Id. I read that there is no way for EF to get back this data. The only way to get the data is to alter the sproc to give it a column name (i.e. SELECT @Id AS Id).

I think that is why the TestResult is still generated; just that it couldn’t find any columns so the class is empty. Btw, I left out the guts of the method that you can find below.

Before:

public virtual async Task<List<TestResult>> TestAsync(...) 
{ 
  // parameters setup
  var _ = await _context.SqlQueryAsync<TestResult>(...);
  return _;
}

After:

public virtual async Task<int> TestAsync(...)
{
  // parameters setup
  var _ = await _context.Database.ExecuteSqlRawAsync(...);
  return _;
}

Everything is fine for me.

[ErikEJ]

Does Test sproc actually return anything? Can you provide a repro sproc?