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How to Retrieve Stored Procedure Output Parameters in Entity Framework

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How to Retrieve Stored Procedure Output Parameters in Entity Framework

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One question that raises from time to  time in EF forums is how you can retrieve stored procedure output parameters in EF Function Import. This post will show you how to do that.


The Stored Procedure

In the example I’m going to use the following stored procedure:

CREATE PROCEDURE dbo.SchoolBudgetForDateRange    @StartDate DATETIME,    @EndDate DATETIME,    @Sum money outputASSET NOCOUNT ON;SELECT @Sum = SUM(Department.Budget)FROM Department WHERE StartDate BETWEEN @StartDate AND @EndDate

The stored procedure returns the school budget for a given date.  By of course the stored procedure could return that calculation without using an output parameter.

Retrieving Stored Procedure Output Parameter

After creating a Function Import (which is explained here) we can use the SchoolBudgetforDateRange method with the context we have. In order to get an output parameter you need to supply an ObjectParameter to the stored procedure call which holds the parameter name and type. After the execution of the stored procedure you can retrieve the parameter using the Value property of the ObjectParameter.  The following code shows how to that exactly what I wrote:

static void Main(string[] args){  using (SchoolEntities context = new SchoolEntities())  {    var outputParameter = new ObjectParameter("sum", typeof(decimal));    context.SchoolBudgetForDateRange(new DateTime(2007, 1, 1),       new DateTime(2008, 1, 1),       outputParameter);    Console.WriteLine(outputParameter.Value);  }}

 

Summary

Once you need to retrieve output parameters from EFFunction Imports, you need to supply an ObjectParameter to hold the output. In the post I showed how to do that.


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Topics:
dotnet ,.net & windows ,entity framework

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