Provide content from a base component that is not overridden

MyBase.cs

public class MyBase : ComponentBase
{
	string someValue = "test";
	public MyBase()
	{
		var rf = typeof(ComponentBase).GetField("_renderFragment", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
		var pqr= typeof(ComponentBase).GetField("_hasPendingQueuedRender", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
		var nr= typeof(ComponentBase).GetField("_hasNeverRendered", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
		rf.SetValue(this, (RenderFragment)(builder =>
		{
			pqr.SetValue(this, false);
			nr.SetValue(this, false);
			builder.OpenComponent<CascadingValue<string>>(1);
			builder.AddAttribute(2, "Value", someValue);
			builder.AddAttribute(3, "ChildContent", (RenderFragment)( builder2 => BuildRenderTree(builder2)));
			builder.CloseComponent();
		}));
	}
}

This will automatically include a CascadingValue for "someValue" to all child components.

If you don't want to use reflection, you can create your own base component that implements everything ComponentBase does, then modify the constructor in a similar way, but directly referencing the fields instead of using reflection.