Optional parameters in ASP.NET web service

Question

I have a ASP.NET web service. This web service works fine. However, the WSDL lists some parameters as optional (minoccurs = 0) and others as non-optional. Some of the optional parameters are actually not optional, others which are marked as non-optional are actually optional. I would like to fix this, but I can't find the location where this information is coming from.

It seems to me that all primitive types (int, boolean etc.) are non-optional and all other parameters are marked as optional. However, I can't find a location where I can change this. I would like to specify default values for the primitive values if they are missing in the request and specify which non-primitive parameter is actually optional. Where do I do this?

Solution 1

I am assuming that when you say ASP.net web services, you are creating web services with ASMX extension. I think that what happens in this case is that all nullable types become optional and non-nullable become non-optional.

You could perhaps manually edit the generated WSDL file. But then you would have to redo that work if the wsdl was regenerated.

I would suggest that you switch to WCF with basisHttpBinding (except for the name of you service your clients should not notice the difference).

Using WCF you can simply mark the parameter in the data contract as required or not:

[DataMember(IsRequired="false")]

Solution 2

The primitives are not reference types, but rather they are value types. You can make a value type "nullable" a couple ways.

The short-hand is

int? i;

or long-hand here

Nullable<int> i;

Comments

[Bora]

This answer is almost completely false. You cannot use nullables instead of optional parameters. Since .Net 4.0 you can use optional parameters in any method.

[Shiraz Bhaiji]

@Bora, the answer is from 2009, at that time this was what was available.

[Bora]

Nothing wrong with that. Just update your answer and everything will be well again.

[Shiv]

How do you distinguish between omitting the parameter (and use a default) vs wanting to set the value to NULL?

[oglester]

I suppose if you want to distinguish this, you might want to migrate to the Functional pattern of Option/Maybe and not allow nulls. In that paradigm, you would have an explicit object type for Null/Empty. How to get ASMX's to change minoccurs in WSDL, I'm just not sure. You might read more here: stackoverflow.com/questions/3961112/…

[oglester]

Also, if you really want your web services to have a pristine XSD/WSDL contract, you can build your web services Contract-first: docs.microsoft.com/en-us/dotnet/framework/wcf/… stackoverflow.com/questions/23000510/…