BASTA 2013: Custom OData Provider
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The document provides an introduction to custom OData providers and IQueryable in the context of database queries. It discusses the architecture, implementation, and usage of custom IQueryable and OData providers, including the necessary interfaces and methods to develop them. Additionally, it outlines how to utilize expression trees for querying and managing data sources effectively.
![IDataServiceQueryProvider
public interface IDataServiceQueryProvider
{
object CurrentDataSource { get; set; }
bool IsNullPropagationRequired { get; }
object GetOpenPropertyValue(object target, string propertyName);
IEnumerable<KeyValuePair<string, object>> GetOpenPropertyValues(
object target);
object GetPropertyValue(object target,
ResourceProperty resourceProperty);
IQueryable GetQueryRootForResourceSet(ResourceSet resourceSet);
ResourceType GetResourceType(object target);
object InvokeServiceOperation(ServiceOperation serviceOperation,
object[] parameters);
}](https://image.slidesharecdn.com/customodataproviders-rainerstropek-130227085058-phpapp02/85/BASTA-2013-Custom-OData-Provider-18-320.jpg)
BASTA 2013: Custom OData Provider
- 1. Rainer Stropek Custom Odata Providers
- 2. Introduction • You all know what OData is? – Short demo to introduce OData? • You are all familiar with LINQ & IQueryable? – Short demo to introduce IQueryable?
- 3. What is the basic idea of OData and IQueryable regarding database queries? ARCHITECTURE
- 4. Architecture of C#, OData and IQueryable Compiler Generator Grammar rules Tree Source Lexer, Parser Generator Target (Syntax Tree) Interpreter
- 5. Architecture of C#, OData and IQueryable C# Compiler BCL C# IL Expression Tree OData Query (URI) SQL OData Entity runtime Framework Interpret or rewrite
- 6. Typical Architecture Clients Load Balancer DB Failover Web Farm Cluster Cloud
- 7. Solution = Sharding Clients Load Balancer DB Load Web Farm Balancing Cluster of Failover Cloud Clusters
- 8. How can we build a custom IQueryable? CUSTOM IQUERYABLE
- 9. Custom IQueryable • Use IQToolkit if possible • Derive your implementation from QueryProvider • Implement two virtual methods – object Execute(Expression expression) – string GetQueryText(Expression expression) (Optional)
- 10. Using Custom IQueryable • Expression tree is received by query provider • We have to rewrite and run it to all e.g. sharding databases
- 11. Implement Queryable • Use .NET‘s visitor pattern to examine and rewrite expression tree • AnalyzeQueryVisitor – Verifies that query is ok (e.g. must contain top-clause, etc.) – Stores reference to e.g. Take and Skip clauses
- 12. How can we build a custom OData provider? CUSTOM ODATA PROVIDER
- 13. Custom OData Building Blocks • Derive from DataService<T> – Main entry point for developing a WCF Data Service • Implement IServiceProvider to provide... – ...IDataServiceMetadataProvider • Build custom metadata • Build OData metadata with e.g. reflection – ... IDataServiceQueryProvider • Provide an underlying IQueryable for query execution
- 14. Workflow for OData Query (simplified) Get metdata service Get query provider Create data- source Set current data source Initialize service Get IQueryable used for getting Provide Resolve resource data metdata set Get query root (IQueryable)
- 15. IDataServiceMetadataProvider • ResourceSet consisting of ResourceType objects (=entity types) • CustomDataServiceMetadataProvider is a simple generic implementation of IDataServiceMetadataProvider
- 16. IDataServiceMetadataProvider public interface IDataServiceMetadataProvider { Service Ops not string ContainerName { get; } covered here string ContainerNamespace { get; } IEnumerable<ResourceSet> ResourceSets { get; } IEnumerable<ServiceOperation> ServiceOperations { get; } IEnumerable<ResourceType> Types { get; } IEnumerable<ResourceType> GetDerivedTypes(ResourceType resourceType); ResourceAssociationSet GetResourceAssociationSet( ResourceSet resourceSet, ResourceType resourceType, ResourceProperty resourceProperty); bool HasDerivedTypes(ResourceType resourceType); bool TryResolveResourceSet(string name, out ResourceSet resourceSet); bool TryResolveResourceType(string name, out ResourceType resourceType); bool TryResolveServiceOperation(string name, out ServiceOperation serviceOperation); }
- 17. IDataServiceQueryProvider • Provides root IQueryable for a given resource set • CustomDataServiceProvider is a simple generic implementation of IDataServiceQueryProvider
- 18. IDataServiceQueryProvider public interface IDataServiceQueryProvider { object CurrentDataSource { get; set; } bool IsNullPropagationRequired { get; } object GetOpenPropertyValue(object target, string propertyName); IEnumerable<KeyValuePair<string, object>> GetOpenPropertyValues( object target); object GetPropertyValue(object target, ResourceProperty resourceProperty); IQueryable GetQueryRootForResourceSet(ResourceSet resourceSet); ResourceType GetResourceType(object target); object InvokeServiceOperation(ServiceOperation serviceOperation, object[] parameters); }
- 19. Linking Custom OData & Custom LINQ Provider