Droptree field source query to filter on base templates

Question

I am looking to add a source to the Droptree field. This is working fine, but the issue is that it allows all the templates under the home item to be added. But I want to limit it to only items which have this Template ID {BC5A3B05-FB72-4DF5-A3A5-D5EEFF51D672} as a base template.

Please note that I am looking to filter base on the base template of the item. I know I can query based on the template itself but I don't know if there is an out of the box way to query on base template.

Answer 1

It doesn't exist OOTB to filter base on the base template of the item.

You need to check the class Sitecore.Shell.Applications.ContentEditor.Tree

the Source method

    /// <summary>Gets or sets the source.</summary>
    /// <value>The source.</value>
    public string Source
    {
      get => StringUtil.GetString(this._source);
      set
      {
        Assert.ArgumentNotNull((object) value, nameof (value));
        if (!value.StartsWith("query:", StringComparison.InvariantCulture))
        {
          this._source = value;
        }
        else
        {
          Item obj1 = Client.ContentDatabase.GetItem(this.ItemID);
          if (obj1 == null)
            return;
          Item obj2 = obj1.Axes.SelectSingleItem(value.Substring("query:".Length));
          if (obj2 == null)
            return;
          this._source = obj2.ID.ToString();
        }
      }
    }

The problem is Sitecore Query Syntax doesn't support filtering based on base template:

https://doc.sitecore.com/SdnArchive/Reference/Using%20Sitecore%20Query/Sitecore%20Query%20Syntax.html