Given I have two c# objects of the same type, I want to compare them to create a JsonPatchDocument.
I have a StyleDetail class defined like this:
public class StyleDetail
{
public string Id { get; set; }
public string Code { get; set; }
public string Name { get; set; }
public decimal OriginalPrice { get; set; }
public decimal Price { get; set; }
public string Notes { get; set; }
public string ImageUrl { get; set; }
public bool Wishlist { get; set; }
public List<string> Attributes { get; set; }
public ColourList Colours { get; set; }
public SizeList Sizes { get; set; }
public ResultPage<Style> Related { get; set; }
public ResultPage<Style> Similar { get; set; }
public List<Promotion> Promotions { get; set; }
public int StoreStock { get; set; }
public StyleDetail()
{
Attributes = new List<string>();
Colours = new ColourList();
Sizes = new SizeList();
Promotions = new List<Promotion>();
}
}
if I have two StyleDetail objects
StyleDetail styleNew = db.GetStyle(123);
StyleDetail styleOld = db.GetStyle(456);
I now want to create a JsonPatchDocument so I can send the differences to my REST API... How to do this??
JsonPatchDocument patch = new JsonPatchDocument();
// Now I want to populate patch with the differences between styleNew and styleOld - how?
in javascript, there is a library to do this https://www.npmjs.com/package/rfc6902
Calculate diff between two objects:
rfc6902.createPatch({first: 'Chris'}, {first: 'Chris', last: 'Brown'});
[ { op: 'add', path: '/last', value: 'Brown' } ]
but I am looking for a c# implementation
Let's abuse the fact that your classes are serializable to JSON! Here's a first attempt at a patch creator that doesn't care about your actual object, only about the JSON representation of that object.
public static JsonPatchDocument CreatePatch(object originalObject, object modifiedObject)
{
var original = JObject.FromObject(originalObject);
var modified = JObject.FromObject(modifiedObject);
var patch = new JsonPatchDocument();
FillPatchForObject(original, modified, patch, "/");
return patch;
}
static void FillPatchForObject(JObject orig, JObject mod, JsonPatchDocument patch, string path)
{
var origNames = orig.Properties().Select(x => x.Name).ToArray();
var modNames = mod.Properties().Select(x => x.Name).ToArray();
// Names removed in modified
foreach (var k in origNames.Except(modNames))
{
var prop = orig.Property(k);
patch.Remove(path + prop.Name);
}
// Names added in modified
foreach (var k in modNames.Except(origNames))
{
var prop = mod.Property(k);
patch.Add(path + prop.Name, prop.Value);
}
// Present in both
foreach (var k in origNames.Intersect(modNames))
{
var origProp = orig.Property(k);
var modProp = mod.Property(k);
if (origProp.Value.Type != modProp.Value.Type)
{
patch.Replace(path + modProp.Name, modProp.Value);
}
else if (!string.Equals(
origProp.Value.ToString(Newtonsoft.Json.Formatting.None),
modProp.Value.ToString(Newtonsoft.Json.Formatting.None)))
{
if (origProp.Value.Type == JTokenType.Object)
{
// Recurse into objects
FillPatchForObject(origProp.Value as JObject, modProp.Value as JObject, patch, path + modProp.Name +"/");
}
else
{
// Replace values directly
patch.Replace(path + modProp.Name, modProp.Value);
}
}
}
}
Usage:
var patch = CreatePatch(
new { Unchanged = new[] { 1, 2, 3, 4, 5 }, Changed = "1", Removed = "1" },
new { Unchanged = new[] { 1, 2, 3, 4, 5 }, Changed = "2", Added = new { x = "1" } });
// Result of JsonConvert.SerializeObject(patch)
[
{
"path": "/Removed",
"op": "remove"
},
{
"value": {
"x": "1"
},
"path": "/Added",
"op": "add"
},
{
"value": "2",
"path": "/Changed",
"op": "replace"
}
]