locked
Why does a stored procedure return ISingleResult instead of Table?

    Question

  • Even when you specify the return type.  What's the point of specifying a return type when it doesn't return that type.  Is there a way to force it to return the same type a table query returns?  Am I missing something here.

    Thursday, December 13, 2007 5:35 AM

Answers

  • Yes. The stored procedure in LinQ to SQL will return ISingleResult type by default. If you would like to return a Table, you can try to refer to the following sample codes for reference:

    CREATE PROCEDURE [dbo].[Customers By City]
        (@param1 NVARCHAR(20))
    AS
    BEGIN
        -- SET NOCOUNT ON added to prevent extra result sets from
        -- interfering with SELECT statements.
        SET NOCOUNT ON;
        SELECT CustomerID, ContactName, CompanyName, City from Customers
            as c where c.City=@param1
    END

     

    [Function(Name="dbo.Customers By City")]
    public ISingleResult<CustomersByCityResult> CustomersByCity([Parameter(DbType="NVarChar(20)")] string param1)
    {
        IExecuteResult result = this.ExecuteMethodCall(this,         ((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
        return ((ISingleResult<CustomersByCityResult>)(result.ReturnValue));
    }

     

    // Call the stored procedure.
    DataTable ReturnResultset()
    {
        Northwnd db = new Northwnd(@"c:\northwnd.mdf");

        ISingleResult<CustomersByCityResult> result =
            db.CustomersByCity("London");

     

        DataTable dt = new DataTable();

        //Create the DataTable structure and add the corresponding columns to it

     

        foreach (CustomersByCityResult cust in result)
        {
            //Fill the DataTable according to the result - ISingleResult<CustomersByCityResult>
        }

        return dt;
    }

     

    Try to check out this document about "How to: Use Stored Procedures to Return Rowsets (LINQ to SQL)" for details - http://msdn2.microsoft.com/en-us/library/bb386975.aspx

    Wednesday, December 19, 2007 8:20 AM

All replies

  • Yes. The stored procedure in LinQ to SQL will return ISingleResult type by default. If you would like to return a Table, you can try to refer to the following sample codes for reference:

    CREATE PROCEDURE [dbo].[Customers By City]
        (@param1 NVARCHAR(20))
    AS
    BEGIN
        -- SET NOCOUNT ON added to prevent extra result sets from
        -- interfering with SELECT statements.
        SET NOCOUNT ON;
        SELECT CustomerID, ContactName, CompanyName, City from Customers
            as c where c.City=@param1
    END

     

    [Function(Name="dbo.Customers By City")]
    public ISingleResult<CustomersByCityResult> CustomersByCity([Parameter(DbType="NVarChar(20)")] string param1)
    {
        IExecuteResult result = this.ExecuteMethodCall(this,         ((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
        return ((ISingleResult<CustomersByCityResult>)(result.ReturnValue));
    }

     

    // Call the stored procedure.
    DataTable ReturnResultset()
    {
        Northwnd db = new Northwnd(@"c:\northwnd.mdf");

        ISingleResult<CustomersByCityResult> result =
            db.CustomersByCity("London");

     

        DataTable dt = new DataTable();

        //Create the DataTable structure and add the corresponding columns to it

     

        foreach (CustomersByCityResult cust in result)
        {
            //Fill the DataTable according to the result - ISingleResult<CustomersByCityResult>
        }

        return dt;
    }

     

    Try to check out this document about "How to: Use Stored Procedures to Return Rowsets (LINQ to SQL)" for details - http://msdn2.microsoft.com/en-us/library/bb386975.aspx

    Wednesday, December 19, 2007 8:20 AM
  • you need to drag'n'drop procedure from server explorer directly to Entity. This way you'll associate stored procedure call with entity type you are expecting to recieve
    Wednesday, December 19, 2007 3:03 PM
  • Didn't mean a datatable I meant the Entity that linq to sql datacontext returns when you specify a table.  Don't understand why you have to go through so many hoops to get that and even dragging the stored procedure to the table doesn't force it to return a table, it still returns ISingleResult unless I'm missing something.  I thought the purpose of being able to use a stored procedure and set the return was to make it compatible with a table select using the datacontext.  Am I missing something here?  Linq to sql is starting to make my life hell.

     

     

     Citizen on the earth wrote:

    Yes. The stored procedure in LinQ to SQL will return ISingleResult type by default. If you would like to return a Table, you can try to refer to the following sample codes for reference:

    CREATE PROCEDURE [dbo].[Customers By City]
        (@param1 NVARCHAR(20))
    AS
    BEGIN
        -- SET NOCOUNT ON added to prevent extra result sets from
        -- interfering with SELECT statements.
        SET NOCOUNT ON;
        SELECT CustomerID, ContactName, CompanyName, City from Customers
            as c where c.City=@param1
    END

     

    [Function(Name="dbo.Customers By City")]
    public ISingleResult<CustomersByCityResult> CustomersByCity([Parameter(DbType="NVarChar(20)")] string param1)
    {
        IExecuteResult result = this.ExecuteMethodCall(this,         ((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
        return ((ISingleResult<CustomersByCityResult>)(result.ReturnValue));
    }

     

    // Call the stored procedure.
    DataTable ReturnResultset()
    {
        Northwnd db = new Northwnd(@"c:\northwnd.mdf");

        ISingleResult<CustomersByCityResult> result =
            db.CustomersByCity("London");

     

        DataTable dt = new DataTable();

        //Create the DataTable structure and add the corresponding columns to it

     

        foreach (CustomersByCityResult cust in result)
        {
            //Fill the DataTable according to the result - ISingleResult<CustomersByCityResult>
        }

        return dt;
    }

     

    Try to check out this document about "How to: Use Stored Procedures to Return Rowsets (LINQ to SQL)" for details - http://msdn2.microsoft.com/en-us/library/bb386975.aspx

    Thursday, December 20, 2007 3:02 AM
  • Our sproc return types are ISingleResult<T> for single result set returning sprocs, and IMultipleResults for sprocs that return multiple result sets.  Sprocs return these types rather than Tables because Table<T> and ISingleResult have different semantics.  For example, an ISingleResult exposes the sproc return value via ISingleResult.ReturnValue, sproc results can only be enumerated a single time, etc. 

     

    In your case, after you've modified your sproc so that it returns ISingleResult<Entity> you can just enumerate over the results.  The entities returned are then identity/change tracked just like results returned from Table<T> queries.

     

    Wednesday, January 02, 2008 7:23 PM
  • They're missing the point of what you're asking, many stored procedures return just one row, so you'd like a simple assignment such as,

     

    //Class has a customer field

    private Customer _customer

     

    void LoadData()

    {

    _customer = _dataContext.GetCustomer(customerID)

    }

     

    Which won't work, nor will _customer = (Customer)_dataContext.GetCustomer(customerID)

    because despite the fact that you assigned GetCustomer the return type of customer, it's still returning an ISingleResult.

     

    Instead you have to a loop or a list with a capacity of 1 and then AddRange(_dataContext.GetCustomer(customerID)).

     

    It's frustrating, and I've tried to code around this situation within the linq datacontext itself, even the compiler generated file, but no matter what you're going to have use a loop or a list with AddRange.

     

    My advice, use a loop and the JIT compiler will factor it out.  Readability suffers with both methods but the JIT compiler can't factor out the explicit declaration of a temporary list like it can factor out a loop.

    Friday, May 30, 2008 5:33 PM
  • Here is the solution to the problem

    the entity class GetCustomerResult is already created for you in the designer so in essence all you are doing here is casting ISingleResult to GetCustomerResult and returning a list of GetCustomerResult.

     

    public static List<GetCustomerResult> GetCustomer1()

    {

    List<GetCustomerResult> results = dataContext.GetCustomer(customerID).ToList<GetCustomerResultResult>();

    return results;

    }

     

    so now what you do is

    yourGrid.DataSource = GetCustomer1();

    yourGrid.DataBind();

     

    It has work for me, no need for foreach loop. waste of time

    • Proposed as answer by Mohammed Owes Thursday, October 20, 2011 12:56 PM
    Wednesday, August 27, 2008 5:22 PM
  • Here's a simple way to access a single rowset and map it to an Entity:

     

    1- In the DataClasses deigner DBML file, right click the Data Function in the right pane and select "Properties"

     

    2- Change the "Return Type" from "(Auto-generated Type)" to your which should be available in the drop down (in my case, the table entity is: md_SimpleAttribute).

     

     

    3- Use the following method to access the first and only item in the result list:

     

    Code Snippet

        public static md_SimpleAttribute GetAttribute(string attributeId, string saType)

        {

          md_SimpleAttribute sa = new md_SimpleAttribute();

          DataClasses1DataContext ctx = new DataClasses1DataContext();

          ISingleResult<md_SimpleAttribute> result = ctx.esp_md_SimpleAttribute_select(attributeId, saType);

          sa = result.ToList<md_SimpleAttribute>()[0];

          return sa;          

        }

     

     

     

     

    Tuesday, September 23, 2008 6:38 PM
  • Great Work... I was stuck up at this position for 4hours and now i got it... Very Thanks to kDamalie
    Thursday, October 20, 2011 12:57 PM

  • I tried the following that works just fine

    I have a sproc called GetCustomerByID that i pass a customer ID to . I know I will have only one record returned from this sproc and I want the results to be of type Customer not Iresult. I created a helper method in my DataContext Class

    public partial class NorthWindDataContext
    {
        public  Customer GetMyCustomer(string customerID)
       {
     List<Customer> myCustomer;
     myCustomer = this.GetCustomerByID(customerID).ToList();

     return myCustomer[0];

        }
    }

    one caveat - when you drag the sproc onto the designer surface drop it on the class you want it to reflect , the method it creates will be: public ISingleResult<Customer> GetCustomerByID if you just drop it in the stored procedure pane it will not be of type customer but rather public ISingleResult<GetCustomerByIDResult> GetCustomerByID
    • Edited by Shlomo77 Thursday, November 17, 2011 7:08 PM
    Thursday, November 17, 2011 6:57 PM