Question

For example, if I have the following json texts:

 object1{
     field1: value1;
     field2: value2;
     field3: value3;
 }

 object1{
     field1: value1;
     field2: newvalue2;
     field3: value3;
 }

I need something in c# that reads that files and shows the difference. i.e. it can return the following object:

differences {
    object1: { field: field2, old_value: value2, new_value: newvalue2}
}

Is there some API or suggestions to do this?

Answer 1

I recommend you use Weakly-Typed JSON Serialization and write a routine that uses JsonObject like this:

String JsonDifferenceReport(String objectName,
                            JsonObject first,
                            JsonObject second)
{
  if(String.IsNullOrEmpty(objectName))
    throw new ArgumentNullException("objectName");
  if(null==first)
    throw new ArgumentNullException("first");
  if(null==second)
    throw new ArgumentNullException("second");
  List<String> allKeys = new List<String>();
  foreach(String key in first.Keys)
    if (!allKeys.Any(X => X.Equals(key))) allKeys.Add(key);
  foreach(String key in second.Keys)
    if (!allKeys.Any(X => X.Equals(key))) allKeys.Add(key);
  String results = String.Empty;
  foreach(String key in allKeys)
  {
    JsonValue v1 = first[key];
    JsonValue v1 = second[key];
    if (((null==v1) != (null==v2)) || !v1.Equals(v2))
    {
      if(String.IsNullOrEmpty(results))
      {
         results = "differences: {\n";
      }
      results += "\t" + objectName + ": {\n";
      results += "\t\tfield: " + key + ",\n";
      results += "\t\toldvalue: " + (null==v1)? "null" : v1.ToString() + ",\n";
      results += "\t\tnewvalue: " + (null==v2)? "null" : v2.ToString() + "\n";
      results += "\t}\n";
    }
  }
  if(!String.IsNullOrEmpty(results))
  {
    results += "}\n";
  }
  return results;
}

Your choice whether to get reports recursively inside JsonValue v1 and v2, instead of just using their string representation as I did here.

If you wanted to go recursive, it might change the above like this:

  if ((null==v1) || (v1.JsonType == JsonType.JsonPrimitive)
   || (null==v2) || (v2.JsonType == JsonType.JsonPrimitive))
  {
    results += "\t\tfield: " + key + ",\n";
    results += "\t\toldvalue: " + (null==v1) ? "null" : v1.ToString() + ",\n";
    results += "\t\tnewvalue: " + (null==v2) ? "null" : v2.ToString() + "\n";
  }
  else
  {
    results + JsonDifferenceReport(key, v1, v2);
  }

-Jesse