PnP.Core.ClientException: Specify the GraphGet/GraphGetLinq field of the ClassMapping property

[SPDEVGUY]

Category

• Bug / Question?

Describe the bug

Unhelpful exception when querying sub-webs:
PnP.Core.ClientException: Specify the GraphGet/GraphGetLinq field of the ClassMapping property

Attempting to follow documentation to enumerate sub-webs:
https://pnp.github.io/pnpcore/using-the-sdk/webs-intro.html#getting-sub-webs

Error thrown:

Source code:

Essential bits:
`
var url = "https://contoso.sharepoint.com";

var context = await Pnp.CreateAsync(new Uri(url));

log.Log($"Loaded context for {ctx.Site.Id}");

var site = ctx.Site;

await site.GetAsync(p => p.RootWeb);

var rw = site.RootWeb;

await rw.GetAsync(p => p.Webs);

foreach (var w in rw.Webs) << Exception accessing rw.Webs property.
`

Steps to reproduce

Code above.
Can I not use PnPContext.Site.RootWeb.Webs with the foreach?

Expected behavior

When accessing Context.Site.RootWeb.Webs I expect to be able to enumerate the webs within that site after doing the GetAsync calls as per the documentation.

Throw informative exception or improve documentation?

Environment details (development & target environment)

• SDK version: 1.4.0
• OS: Win10
• SDK used in: Console app, .NET Framework 4.7.2
• Framework: .NET Framework 4.7.2
• Browser(s): Chorme?
• Tooling: VS2019
• Additional details: None.

Additional context

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[jansenbe]

@SPDEVGUY : Once you've loaded data you need to use .AsRequested() to query the loaded data...in your case you're trying to query twice. The documentation was still missing AsRequested() thanks for spotting that.

So your code would be like this:

var url = "https://contoso.sharepoint.com";
var context = await Pnp.CreateAsync(new Uri(url));
log.Log($"Loaded context for {ctx.Site.Id}");
var site = ctx.Site;
await site.GetAsync(p => p.RootWeb);
var rw = site.RootWeb;
await rw.GetAsync(p => p.Webs);

foreach (var w in rw.Webs.AsRequested())
{
}

You could also optimize above code a little bit as rootweb is always loaded by default + possibly you can save a roundtrip by loading additional RootWeb properties during PnPContext initialization (see https://pnp.github.io/pnpcore/using-the-sdk/basics-context.html). Taking that in account below code will do 2 server roundtrips to achieve the same result:

var options = new PnPContextOptions()
{
    AdditionalWebPropertiesOnCreate =
        new Expression<Func<IWeb, object>>[]
        {
            w => w.Webs
        }
};

var url = "https://contoso.sharepoint.com";
var context = await Pnp.CreateAsync(new Uri(url), options);

log.Log($"Loaded context for {ctx.Site.Id}");

foreach (var w in context.Web.Webs.AsRequested())
{
  // Use the web
}

[s-KaiNet]

I think still we have an issue here, because below code throws an exception:

var webs = context.Web.Webs.ToList();

To my understanding, it shouldn't throw and should query subwebs instead.

[jansenbe]

@s-KaiNet : Yes, I know...something to still be fixed. For @SPDEVGUY 's case however the provided code is a good alternative, but I do agree that this should be fixed to ensure a consist experience across the various models

[jansenbe]

@s-KaiNet , @SPDEVGUY : I've also pushed a fix that enables using LINQ (context.Web.Webs.ToList() or foreach (var w in rw.Webs) { } ). Think this issue can be closed now.