TechNet Express: How to Implement Language Translation in WCF Data Service (OData) Part-2

In Part-1 of this post I explained language translation via <QueryView> and Entity Join approach that is suggested for scenario having just one translation table. This article present a generic approach that can be used with multiple translation tables

Problem :-

Lets assume you have a Product Entity and and it has one fields that need to be translated. For simplicity I am Just using one table. Step by step solution is below

Solution

Create your Main Table in EDMX and add the additional property (Translated Name)
Also import all the translation tables

In order support additional property you either you need <DefiningQuery> or <QueryView> element to explicitly supply select query. This solution uses <QueryView>. See additional Null in query view.

select value

NORTHWNDModel.Product

(p.ProductID,

p.ProductName,

null,

p.SupplierID,

p.CategoryID,

p.QuantityPerUnit,

p.UnitPrice,

p.UnitsInStock,

p.UnitsOnOrder,

p.ReorderLevel,

p.Discontinued

)

from NORTHWNDModelStoreContainer.Products as p

</QueryView>

</EntitySetMapping>

Override "OnStartProcessingRequest" in data service class

protected override void OnStartProcessingRequest(ProcessRequestArgs args)

{

this.CurrentDataSource.ObjectMaterialized += new System.Data.Objects.ObjectMaterializedEventHandler(CurrentDataSource_ObjectMaterialized);

base.OnStartProcessingRequest(args);

}

Implement ObjectMaterialized even to do actual translation

void CurrentDataSource_ObjectMaterialized(object sender, System.Data.Objects.ObjectMaterializedEventArgs e)

{

//This code uses hardecoded language parameter but if you want to pass it

// dynamicly use query paramteters

// see http://ashwini47-tts.blogspot.in/2012/03/how-to-parametrized-queryinterceptor-in.html

string language = "IT-IT";

var entities = this.CurrentDataSource;

if (e.Entity.GetType() == typeof(Product))

{

Product entity = (Product)e.Entity;

var translation = from code in entities.NameTranslations

where (entity.ProductID==code.ProductID &&

code.Language == language)

select code;

if (translation.Count()>0)

{

entity.ProductTranslatedName = translation.First().ProductNativeName;

}

else

{

entity.ProductTranslatedName = "Not Found";

}

Navigate to your service URL to see the result

-<m:properties>

<d:ProductID m:type="Edm.Int32">1</d:ProductID>

<d:ProductName>Chai</d:ProductName>

<d:ProductTranslatedName xml:space="preserve">IT_Chai</d:ProductTranslatedName>

<d:SupplierID m:type="Edm.Int32">1</d:SupplierID>

<d:CategoryID m:type="Edm.Int32">1</d:CategoryID>

<d:QuantityPerUnit>10 boxes x 20 bags</d:QuantityPerUnit>

<d:UnitPrice m:type="Edm.Decimal">18.0000</d:UnitPrice>

<d:UnitsInStock m:type="Edm.Int16">39</d:UnitsInStock>

<d:UnitsOnOrder m:type="Edm.Int16">0</d:UnitsOnOrder>

<d:ReorderLevel m:type="Edm.Int16">10</d:ReorderLevel>

<d:Discontinued m:type="Edm.Boolean">false</d:Discontinued>

</m:properties>

- <m:properties>

<d:ProductID m:type="Edm.Int32">3</d:ProductID>

<d:ProductName>Aniseed Syrup</d:ProductName>

<d:ProductTranslatedName>Not Found</d:ProductTranslatedName>

<d:SupplierID m:type="Edm.Int32">1</d:SupplierID>

<d:CategoryID m:type="Edm.Int32">2</d:CategoryID>

<d:QuantityPerUnit>12 - 550 ml bottles</d:QuantityPerUnit>

<d:UnitPrice m:type="Edm.Decimal">10.0000</d:UnitPrice>

<d:UnitsInStock m:type="Edm.Int16">13</d:UnitsInStock>

<d:UnitsOnOrder m:type="Edm.Int16">70</d:UnitsOnOrder>

<d:ReorderLevel m:type="Edm.Int16">25</d:ReorderLevel>

<d:Discontinued m:type="Edm.Boolean">false</d:Discontinued>

</m:properties>

Suggested

Extract Language parameter dynamically.
Querying database for each row in "CurrentDataSource_ObjectMaterialized" handler could be a big performance hit especially in case of large tables. I would suggest to implement caching of entire translation table at once. I will try to post another article on it once I have time.

Limitation