Return Custom Object <List T> from Entity framework and assign to Object Data Source
Solution 1
what about something like this:
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
string myQuery = @"SELECT p.ProductID, p.Name FROM
AdventureWorksEntities.Products as p";
foreach (DbDataRecord rec in new ObjectQuery<DbDataRecord>(myQuery, context))
{
Console.WriteLine("ID {0}; Name {1}", rec[0], rec[1]);
}
}
Solution 2
If you already have an Entity type that matches your proc return type, use it as the type parameter.
public List<MyEntity> GetData<MyEntity>(int product_id) where T : class
{
List<MyEntity> myList = new List<MyEntity>();
var groupData = context.ExecuteStoreQuery<MyEntity>("exec
spGetProductsByGroup @ProductID={0}", product_id);
return myList;
}
Otherwise you could use an ADO.NET DataReader to build the list manually.
using (SqlConnection connection = new SqlConnection("your connection string"))
{
SqlCommand command = new SqlCommand(
"exec spGetProductsByGroup @ProductID",
connection);
command.Parameters.Add(product_id);
connection.Open();
SqlDataReader reader = command.ExecuteReader();
List<ProcType> list = new List<ProcType>();
if (reader.HasRows)
{
while (reader.Read())
{
list.Add(new ProcType(){Property1 = reader.GetInt32(0), Property1 = reader.GetString(1));
}
}
reader.Close();
return list;
}
Shokwave
Updated on July 09, 2022Comments
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Shokwave almost 2 years
I need some guidance with an issue, I am using Entity Framework 4.0, I have a DAL and BLL and am binding to ObjectDataSource on the page.
I had to write a stored procedure using
PIVOT
and dynamic SQL to return the data from multiple entities the way I want. Now I am trying to figure out how can I get Entity Framework to return a custom object that I can bind to myObjectDataSource
on the page, I NEED to use a custom object or a dynamic object since the stored procedure can return any number of columns so I can't use a strongly typed class or entity and I need to be also able to bind this with anObjectDataSource
.Can someone point out a good way to do this and how to define my function? With some code examples please.
I read that I should try to use
List<T>
for returning an object since EF does not support returning datatables/datasets, I have the following so far but I know this isn't correct.I have not worked with generics much, if you could point out how to do this I'm sure this would be helpful for a lot of people. Please provide code examples for the function and how to bind
ObjectDataSource
to the return object?Your help is greatly appreciated!!
Thanks for your help Richard this is what my function looks like right now based on your suggestion for using DbDataRecord
C# function for
ObjectDataSource
in DALpublic List<DbDataRecord> GetData(int product_id) { List<DbDataRecord> availableProducts = new List<DbDataRecord>(); var groupData = context.ExecuteStoreQuery<DbDataRecord>("exec spGetProducts @ProductID={0}", product_id); availableProducts = groupData.ToList<DbDataRecord>(); return availableProducts; }
ObjectDataSource
in ASPX page<asp:ObjectDataSource ID="ODSProductAvailability" runat="server" TypeName="Project.BLL.ProductBL" SelectMethod="GetData" > <SelectParameters> <asp:SessionParameter Name="product_id" SessionField="ProductID" /> </SelectParameters> </asp:ObjectDataSource>
Right now I'm getting this error when I access the page:
The result type 'System.Data.Common.DbDataRecord' may not be abstract and must include a default constructor
Is this because the
ExecuteStoreQuery
expects to be defined class or entity? How can I just create an object based on the stored procedure results and assign it that? -
Shokwave over 12 yearsNo thats the problem the stored proc gets data from multiple entities and displays it in a different format, I cant return it with an Entity Type, do you have any examples of using Datareader like you mentioned? or is there a better way to generate customObject from the proc return results?
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jrummell over 12 yearsI'm not sure about using a non Entity type, but I added a DataReader example. See the link above for more general examples.
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Shokwave over 12 yearsThanks for your reply Richard I tried to do your suggestion for var myList = context.ExecuteStoreQuery<DbDataRecord>("exec spGetProductsByGroup @ProductID={0}", product_id); but it gives me an error saying The result type 'System.Data.Common.DbDataRecord' may not be abstract and must include a default constructor. I am not using WPF btw, this is an ASP.net page, please see my post above for an update for the function and Object Data source so you know what I have, thanks again for your help
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Richard Harrison over 12 years@Shokwave to create the list do availableProducts = groupData.ToList(); - you don't need to tell it the type it will figure it out.
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Shokwave over 12 yearsOk thats good but what does the function's signature look like in the DAL class and Business layer class? so far I have tried List<T> GetProductsByGroup<T>(int client_id) and List<T> GetAvailabilityByCarGroups<T>(int client_id) where T : DbDataRecord but none of these work
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Richard Harrison over 12 yearsList<DbDataRecord> GetSomeData()
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Shokwave over 12 yearsI tried the function signature like you mentioned and it still gives me the following error var myList = context.ExecuteStoreQuery<DbDataRecord>("exec spGetProductsByGroup @ProductID={0}", product_id); gives me an error saying The result type 'System.Data.Common.DbDataRecord' may not be abstract and must include a default constructor, I even tried using context.ExecuteStoreQuery<dynamic>>("exec spGetProductsByGroup @ProductID={0}", product_id); as well and it builds fine but the page throws an error object refernce could not be found