Typically when dealing with a Salesforce hosted web service you need to first authenticate to the login site to get a sessionId and Url of the server that will process the requests.
It turns out that it is possible to invoke a web service without this authentication step provided it is configured in a certain way.
Step 1
Mark the class as global and the web service as public. E.g.
/*
* Test to see if the web service can be connected to and used
* without having to log in as there is no api sObject use here.
*/
global class HelloWorld
{
WebService public static String GetMessage()
{
return 'Hello world';
}
}
Step 2
In Salesforce, it is important to give public access to the class (Adding the class under Settings > Develop > Sites > Public Access Settings)
Step 3
Download and import the WSDL from the Apex class.
Step 4
Once you have imported the WSDL you will need to use the public URL of the web service rather than the standard version which requires a session to be established first.
E.g. The domain will change to use the a pattern like:
https://<yourcompanyinsites>.<sandboxname>.<sandboxinstance>.force.com/<sitename>
https://<yourcompanyinsites>.secure.force.com/<sitename>
Step n+1
One of the key aspects when calling it from C# is setting ServicePointManager.Expect100Continue before creating the web service proxy. E.g.
System.Net.ServicePointManager.Expect100Continue = false;
See:
