Delegates, lambdas and Func - c#-4.0

Question

I have a case where I need to call several different web endpoints and need to do the same setup and tear down for every call. I am trying to write a more generic method where I can pass in the method I want to execute along with the package to send to the endpoint and expect a string return.
From my code I can make this call:
var ret = WebServiceHandler.Execute(WebServiceHandler.LoadNewAsset(package));
The definition of Execute looks like:
internal static string Execute<T>(Func<T, string> executeThisAction)
{
Func<T, string> resp;
Setup();
resp = executeThisAction;
CleanUp();
return resp.ToString();
}
This is one of the methods I want to execute:
internal static Func<CarsWS_AssetLoad, string> LoadNewAsset(AssetLoad package)
{
string resp;
try
{
// Make the web service call...
var assetLoadReturn = _service.LoadNewAsset(new LoadNewAssetRequest {UserCredentialsHeader = _credentials, asset = package});
// Evaluate results...
if (assetLoadReturn.LoadNewAssetResult.responseType == "Success")
resp = (result != null && !String.IsNullOrEmpty(result.asset.assetID))
? "Got assetID: " + result.asset.assetID
: "No assetID returned.";
else
resp = result.responseDescription.Trim();
}
catch (Exception ex)
{
resp = "Error calling LoadNewAsset()." + Environment.NewLine + ex.GetFullMessage();
}
return resp; // <== THIS IS NOT A VALID RETURN <== //
}
My brain is shutting off at this point. How do I return the string back up the call stack correctly???

Answer 1

I assume that in your LoadNewAsset method the CarsWS_AssetLoad class is actually the same as AssetLoad and it was just a editing issue with your question.
That being the case, I think this is what you want:
internal static string Execute<T>(Func<T, string> executeThisAction, AssetLoad package)
{
string resp;
Setup();
resp = executeThisAction(package);
CleanUp();
return resp;
}
internal static Func<AssetLoad, string> LoadNewAsset()
{
return package =>
{
string resp;
var assetLoadReturn = _service.LoadNewAsset(new LoadNewAssetRequest {UserCredentialsHeader = _credentials, asset = package});
if (assetLoadReturn.LoadNewAssetResult.responseType == "Success")
resp = (result != null && !String.IsNullOrEmpty(result.asset.assetID))
? "Got assetID: " + result.asset.assetID
: "No assetID returned.";
else
resp = result.responseDescription.Trim();
return resp;
};
}
The use of the variable result in the LoadNewAsset is a little confusing too. Did you mean to use LoadNewAsset instead?
The above code should be able to workable for you, but it's really not the right way to go about coding this.
I assume that the Setup & CleanUp code is all about instantiating the _service that you're calling?
So the key is to code it this way:
internal static string Execute<T>(Func<IAssetService, T, string> serviceCall, AssetLoad package)
{
string resp;
var service = Setup();
resp = serviceCall(service, package);
CleanUp(service);
return resp;
}
internal static Func<IAssetService, AssetLoad, string> GetLoadNewAssetFunc()
{
return (service, package) =>
{
string resp;
var assetLoadReturn = service.LoadNewAsset(new LoadNewAssetRequest {UserCredentialsHeader = _credentials, asset = package});
if (assetLoadReturn.LoadNewAssetResult.responseType == "Success")
resp = (result != null && !String.IsNullOrEmpty(result.asset.assetID))
? "Got assetID: " + result.asset.assetID
: "No assetID returned.";
else
resp = result.responseDescription.Trim();
return resp;
};
}
Ideally if you would bring the Setup & CleanUp code into the Execute method so that the only way to call the set-up and clean-up code is thru the Execute method.
Even better, if the service class implements IDisposable then your execute code would look like this:
internal static string Execute<T>(Func<IAssetService, T, string> serviceCall, AssetLoad package)
{
using (var service = Setup())
{
return serviceCall(service, package);
}
}
Let me know if I've missed anything.

Answer 2

Replace:
internal static string Execute<T>(Func<T, string> executeThisAction)
with
internal static string Execute<T>(Func<T, string> executeThisAction, T argument)
then replace:
internal static Func<CarsWS_AssetLoad, string> LoadNewAsset(AssetLoad package)
with
internal static string LoadNewAsset(AssetLoad package)
then to call it:
var ret = WebServiceHandler.Execute(WebServiceHandler.LoadNewAsset, package);