An aggregation operation computes a single value from a collection of values. An example of an aggregation operation is the calculating of the average daily temperature from a month's worth of daily temperature values. This topic shows how to group orders' details by CustomerID and get the average unit price for each CustomerID.
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To run the code in this example, you need to create a new Telerik OpenAccess Domain Model based on the Northwind database. |
The following code is the LINQ example.
| C# |
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using ( EntitiesModel dbContext = new EntitiesModel() )
{
var query = from orderDetail in dbContext.OrderDetails
group orderDetail by orderDetail.Order.CustomerID into o
select new
{
CustomerID = o.Key,
AverageUnitPrice = o.Average( od => od.UnitPrice )
};
foreach ( var item in query )
{
Console.WriteLine( "CustomerID = {0} \t Average UnitPrice = {1}",
item.CustomerID, item.AverageUnitPrice );
}
} |
| VB.NET |
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Using dbContext As New EntitiesModel()
Dim query = From orderDetail In dbContext.OrderDetails
Group orderDetail By orderDetail.Order.CustomerID Into o = Group
Select New With {Key .CustomerID = CustomerID, Key .AverageUnitPrice = o.Average(Function(od) od.UnitPrice)}
For Each item In query
Console.WriteLine("CustomerID = {0} " & vbTab & " Average UnitPrice = {1}", item.CustomerID, item.AverageUnitPrice)
Next item
End Using |
See Also