Getting data from stored procedure with Entity Framework

Question

I am trying to get the content a table with a dynamic SQL stored procedure called from the database context object (using Entity Framework 6.1.1), in order to populate a GridView control. I fail to retrieve the data.

Here's the stored procedure. It is for a student demonstration about SQL injection in stored procedures, so I KNOW this is inject-able and it's fine.

ALTER PROCEDURE dbo.SearchProducts
  @SearchTerm VARCHAR(max)
AS
BEGIN
  DECLARE @query VARCHAR(max)
  SET @query = 'SELECT * FROM dbo.Products WHERE Name LIKE ''%' + @SearchTerm + '%'''
  EXEC(@query)
END

The C# code behind I then use to execute the stored procedure is :

var db = new MyEntities();
var TEST_SEARCH_TERM = "product";
var result = db.SearchProducts(TEST_SEARCH_TERM);

MyGridView.DataSource = result;
MyGridView.DataBind();

When executed, in the Database Explorer in Visual Studio, the stored procedure works fine. But when executed in the running ASP.NET app, I get an exception in the DataBind() method because result returns -1 instead of an IEnumerable DataSet containing the objects resulting from the stored procedure's SELECT.

How can I retrieve the data and populate my GridView?

Answer 1

Use the following steps to solve this issue:

1. You need to Import the stored procedure as a Function. Right-click on the workspace area of your Entity model and choose Add -> Function Import.
2. In the Add Function Import dialog, enter the name you want your stored procedure to be referred to in your model for example Search_Products, choose your procedure from the drop down list, and choose the return value of the procedure to be Entities and choose Products from the drop down list.

3. Then in the code behind:

   var db = new MyEntities();
   var TEST_SEARCH_TERM = "product";
   var result = db.Search_Products(TEST_SEARCH_TERM);//Search_Products is the name that you specified in Function Import dialog
   
   MyGridView.DataSource = result;
   MyGridView.DataBind();
   

The reason that you get -1 for result is that Entity Framework cannot support Stored Procedure Return values out of the box. I think support of stored procedure return values depends on version of Entity framework. Also Entity Framework doesn't have rich stored procedure support because its an ORM, not a SQL replacement.

Answer 2

I have come across this before with stored procedures using dynamic SQL. I have had success using complex types if I add the line 'SET FMTONLY OFF;' (see https://msdn.microsoft.com/en-us/library/ms173839.aspx) to the top of my stored procedure before it is added to the EF model. Once you have your model setup with your complex type, be sure to remove this line.

Example:

ALTER PROCEDURE dbo.SearchProducts
  @SearchTerm VARCHAR(max)
AS
BEGIN
  SET FMTONLY OFF;
  DECLARE @query VARCHAR(max)
  SET @query = 'SELECT * FROM dbo.Products WHERE Name LIKE ''%' + @SearchTerm + '%'''
  EXEC(@query)
END

Answer 3

Verify that your EDMX has a return type: Go to Function Imports --> SearchProducts, and double click it.

In order to utilize a Complex return type, Entity Framework will require that you explicitly define column names in your stored procedure instead of using *.

Once your stored procedure is modified to define the column names, you can update your model in the project. (Note, performing a complete drop of the SP, and then adding it back to your edmx may be the best route.)

EDIT

Maybe you can modify your SP like the following:

ALTER PROCEDURE dbo.SearchProducts
  @SearchTerm VARCHAR(max)
AS
BEGIN
  SELECT * FROM dbo.Products WHERE Name LIKE '%' + @SearchTerm + '%'
END

Answer 4

You seem to have sorted your problem out, there is official documentation from Microsoft available at the links below:

How to import a stored procedure into your entity data model: https://msdn.microsoft.com/en-us/library/vstudio/bb896231(v=vs.100).aspx

Complex types in the EF designer: https://msdn.microsoft.com/en-gb/data/jj680147.aspx

Make sure you are working with the latest version of .net and you keep your model up to date when you make changes to your database.