ArcGIS Pro 2.7 API Reference Guide
LayerDocument Class
Members  Example 

ArcGIS.Desktop.Mapping Namespace : LayerDocument Class
Represents the content of a .lyrx file that contains one or more layers, all their properties including binary references etc.
Object Model
LayerDocument ClassCIMLayerDocument Class
Syntax
public class LayerDocument : Document 
Public Class LayerDocument 
   Inherits Document
Example
Create a layer from a .lyrx file.
var lyrDocFromLyrxFile = new LayerDocument(@"d:\data\cities.lyrx");
var cimLyrDoc = lyrDocFromLyrxFile.GetCIMLayerDocument();

//modifying its renderer symbol to red
var r = ((CIMFeatureLayer)cimLyrDoc.LayerDefinitions[0]).Renderer as CIMSimpleRenderer;
r.Symbol.Symbol.SetColor(new CIMRGBColor() { R = 255 });

//optionally save the updates out as a file
lyrDocFromLyrxFile.Save(@"c:\data\cities_red.lyrx");

//get a json representation of the layer document and you want store away...
var aJSONString = lyrDocFromLyrxFile.AsJson();

//... and load it back when needed
lyrDocFromLyrxFile.Load(aJSONString);
cimLyrDoc = lyrDocFromLyrxFile.GetCIMLayerDocument();

//create a layer and add it to a map
var lcp = new LayerCreationParams(cimLyrDoc);
var lyr = LayerFactory.Instance.CreateLayer<FeatureLayer>(lcp, map, LayerPosition.AutoArrange);
Inheritance Hierarchy

System.Object
   ArcGIS.Desktop.Mapping.Document
      ArcGIS.Desktop.Mapping.LayerDocument

Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

LayerDocument Members
ArcGIS.Desktop.Mapping Namespace