What determines how DataSourceItem is set in Glass Mapper when used with SitecoreService.GetItem?

Question

I am working on some code that was written years ago and I am just trying to understand how it works. On some pages, there is the following code:

        var context = new SitecoreService(Sitecore.Context.Database.Name);
        item = context.GetItem<ISomething>(DataSourceItem);

I'm trying to determine how the value DataSourceItem is populated - it is not set by my code explicitly. A full search of my code never shows it being set; plus, it doesn't have a 'set' accessor anyway. The question is: for each rendered page, how does Glass Mapper determine the value it should be set to?

If I follow it to it's source, it's in an abstract class that appears auto-generated:

    // Summary:
    //     Returns the item specificed by the data source only. Returns null if no datasource
    //     set
    public Item DataSourceItem { get; }

If I debug the code, the value of DataSourceItem is a GUID that I can easily find in the content editor of Sitecore. Where is this variable populated? I've searched the code, Google, the Sitecore community, and elsewhere. Should be simple, right?

Edit: A couple of people are suggesting that I decompile the Glass Mapper code to see where the value of DataSourceItem is set. Also, a search of my entire codebase doesn't show that this variable is set by my code.

What I really want to know is what determines how DataSourceItem is set. This variable is being set internally by Glass Mapper, but something must have been passed in to it, instructing Glass Mapper to pull an item from Sitecore. I don't see that in the code.

Answer 1

If you check the DLL Glass.Mapper.Sc.Web.Mvc, you will find the implementation of this under GlassController

/// <summary>
/// Returns the item specificed by the data source only. Returns null if no datasource set
/// </summary>
[ExcludeFromCodeCoverage]
public virtual Item DataSourceItem => !this.RenderingContextWrapper.HasDataSource ? (Item) null : Sitecore.Context.Database.GetItem(this.RenderingContextWrapper.GetDataSource());

And if you check the method GetDataSource(), you will find it's implementation.

    public string GetDataSource()
    {
      string dataSource = RenderingContext.CurrentOrNull.Rendering.DataSource;
      if (dataSource.IsNullOrWhiteSpace() && RenderingContext.Current.Rendering.Item != null)
        dataSource = RenderingContext.Current.Rendering.Item.ID.ToString();
      return dataSource;
    }

The above implementation is getting the rendering datasource.

Hope this makes sense.

Thanks

Answer 2

I checked into the code about this property.

public Item DataSourceItem { get; }

Above property returns the RenderingContext.CurrentOrNull.Rendering.DataSource as an item.

You can find more details in Glass.Mapper.Sc.Mvc.dll code. You can use dotPeek to decompile code.

Hope this helps.