Service contracts

The service contract explains what your service can do. It's built using a .NET interface class and decorated with WCF attributes that identify it as a service contract. A basic service contract looks like this:

[ServiceContract()]
public interface IVendorContract
{
[OperationContract()]
void InsertVendor(string vendorId, string vendorName);
[OperationContract()]
bool DeleteVendor(string vendorId);
}

Notice that the interface has a ServiceContract attribute and each operation that we wish to expose publicly on our contract has an OperationContract attribute. Each of these metadata attributes has a series of optional parameters that let us explicitly define public characteristics of the service. For instance, we can add the Name and Namespace properties to the ServiceContract to better characterize this service in our environment. We can also add a series of properties to the OperationContract to control what the operation is named and the SOAPAction value is set to. Why give an alternate name to a service operation? Consider scenarios where you have an overloaded operation in your WCF service contract, and need each WSDL operation to have a unique public name. C# (and .NET) support overloading, but the WSDL standard no longer does.

[ServiceContract(Name="VendorService", Namespace="http://Seroter.BizTalkSOA/Contracts")]
public interface IVendorContract
{
 [OperationContract(Name="InsertVendor")] 
void InsertVendor(string vendorId, string vendorName);
 [OperationContract(Name="InsertVendorWithContact")] 
void InsertVendor(string vendorId, string vendorName, string vendorContactName);
[OperationContract(Name="DeleteVendor")]
bool DeleteVendor(string vendorId);
}

Data contracts

As you can probably imagine, services often need to accept and return comprehensive data entities in addition to simple type parameters. I might want to model a data entity such as a customer instead of having a service operation accept 15 individual string parameters. Complex data parameters are categorized as data contracts in WCF. A data contract is a .NET class object decorated with the DataContract attribute and whose public properties are flagged with DataMember attributes. Public service operation definitions can only include complex types identified as data contracts.

[DataContract()]
public class VendorType
{
private string vendorId;
private string vendorName;
private string vendorContactName;
[DataMember()]
public string VendorId
{
get { return vendorId; }
set { vendorId = value; }
}
[DataMember()]
public string VendorName
{
get { return vendorName; }
set { vendorName = value; }
}
[DataMember()]
public string VendorContactName
{
get { return vendorContactName; }
set { vendorContactName = value; }
}
}

Much like the service contract, the attributes of the data contract allow for more fine-grained control of the entity definition. For instance, we may provide a Name and Namespace to the DataContract , while also adding some useful node ordering and existence attributes to the member elements.

 [DataContract(Name="Vendor" Namespace = "http://Seroter.BizTalkSOA/Types")] 
public class VendorType
{
private string vendorId;
private string vendorName;
private string vendorContactName;
 [DataMember(IsRequired=true, Order=0)] 
public string VendorId
{
get { return vendorId; }
set { vendorId = value; }
}
[DataMember(IsRequired=true, Order=1)]
public string VendorName
{
get { return vendorName; }
set { vendorName = value; }
}
[DataMember(IsRequired=false, Order=2)]
public string VendorContactName
{
get { return vendorContactName; }
set { vendorContactName = value; }
}
}

If you omit the Order property from the DataMember attribute, then the nodes are ordered alphabetically, which may not be how you wish to organize your public schema.