Composable function in client

Applies To: # OData Webapi for Webapi supported OData AspNet WebApi V6

Composable function (function import) can have additional path segments and query options as appropriate for the returned type.

Unbound composable function

For example, we have model:

<Function Name="GetAllProducts" IsComposable="true">
  <ReturnType Type="Collection(NS.Product)" Nullable="false" />
</Function>
<Action Name="Discount" IsBound="true" EntitySetPath="products">
  <Parameter Name="products" Type="Collection(NS.Product)" Nullable="false" />
  <Parameter Name="percentage" Type="Edm.Int32" Nullable="false" />
  <ReturnType Type="Collection(NS.Product)" Nullable="false" />
</Action>
...
<FunctionImport Name="GetAllProducts" Function="NS.GetAllProducts" EntitySet="Products" IncludeInServiceDocument="true" />

GetAllProducts is a function import and it is composable. And since action Discount accepts what GetAllProducts returns, we can query Discount after GetAllProducts.

1. Create function query

var products = Context.CreateFunctionQuery<Product>("", "GetAllProducts", true).Execute();

And we can append query option to the function. For example:

var products = Context.CreateFunctionQuery<ProductPlus>("", "GetAllProducts", true).AddQueryOption("$select", "Name").Execute();

The actual query would be:

GET https://localhost/GetAllProducts()?$select=Name

2. With codegen

With OData client generator, proxy class for function and action would be auto generated. For example:

var getAllProductsFunction = Context.GetAllProductsPlus();
var products = getAllProductsFunction.Execute();   // Get products 
var discdProducts = getAllProductsFunction.DiscountPlus(50).Execute();   // Call action on function
var filteredProducts = getAllProductsFunction.Where(p => p.SkinColorPlus == ColorPlus.RedPlus).Execute();   //Add query option 

Bound composable function

Bound composable function has similiar usage, except that it is tied to a resource.

For example, we have model:

<Function Name="GetSeniorEmployees" IsBound="true" EntitySetPath="People" IsComposable="true">
    <Parameter Name="employees" Type="Collection(NS.Employee)" Nullable="false" />
    <ReturnType Type="NS.Employee" />
</Function>
<Function Name="GetHomeAddress" IsBound="true" IsComposable="true">
    <Parameter Name="person" Type="NS.Person" Nullable="false" />
    <ReturnType Type="NS.HomeAddress" Nullable="false" />
</Function>

Person is the base type of Employee. Then a sample query is:

(Context.People.OfType<Employee>() as DataServiceQuery<Employee>).GetSeniorEmployees().GetHomeAddress().GetValue();