How would you compare two XML Documents?

Question

As part of the base class for some extensive unit testing, I am writing a helper function which recursively compares the nodes of one XmlDocument object to another in C# (.NET). Some requirements of this:

The first document is the source, e.g. what I want the XML document to look like. Thus the second is the one I want to find differences in and it must not contain extra nodes not in the first document.
Must throw an exception when too many significant differences are found, and it should be easily understood by a human glancing at the description.
Child element order is important, attributes can be in any order.
Some attributes are ignorable; specifically xsi:schemaLocation and xmlns:xsi, though I would like to be able to pass in which ones are.
Prefixes for namespaces must match in both attributes and elements.
Whitespace between elements is irrelevant.
Elements will either have child elements or InnerText, but not both.

While I'm scrapping something together: has anyone written such code and would it be possible to share it here?

On an aside, what would you call the first and second documents? I've been referring to them as "source" and "target", but it feels wrong since the source is what I want the target to look like, else I throw an exception.

Danimal_2757 · Answer

Microsoft has an XML diff API that you can use.

Unofficial NuGet: https://www.nuget.org/packages/XMLDiffPatch.

user_823680 · Answer

For comparing two XML outputs in automated testing I found XNode.DeepEquals.

Compares the values of two nodes, including the values of all descendant nodes.

Usage:

var xDoc1 = XDocument.Parse(xmlString1);
var xDoc2 = XDocument.Parse(xmlString2);

bool isSame = XNode.DeepEquals(xDoc1.Document, xDoc2.Document);
//Assert.IsTrue(isSame);

Reference: https://docs.microsoft.com/en-us/dotnet/api/system.xml.linq.xnode.deepequals?view=netcore-2.2

user_10415 · Answer

Comparing XML documents is complicated. Google for xmldiff (there's even a Microsoft solution) for some tools. I've solved this a couple of ways. I used XSLT to sort elements and attributes (because sometimes they would appear in a different order, and I didn't care about that), and filter out attributes I didn't want to compare, and then either used the XML::Diff or XML::SemanticDiff perl module, or pretty printed each document with every element and attribute on a separate line, and using Unix command line diff on the results.

user_3559462 · Answer

All above answers are helpful but I tried XMLUnit which look's easy to use Nuget package to check difference between two XML files, here is C# sample code

public static bool CheckXMLDifference(string xmlInput, string xmlOutput)
    {
        Diff myDiff = DiffBuilder.Compare(Input.FromString(xmlInput))
            .WithTest(Input.FromString(xmlOutput))
            .CheckForSimilar().CheckForIdentical()
            .IgnoreComments()
            .IgnoreWhitespace().NormalizeWhitespace().Build();

        if(myDiff.Differences.Count() == 0)
        {
            // when there is no difference 
            // files are identical, return true;
            return true;
        }
        else
        {
            //return false when there is 1 or more difference in file
            return false;
        }

    }

If anyone want's to test it, I have also created online tool using it, you can take a look here

https://www.minify-beautify.com/online-xml-difference

user_6376513 · Answer

I solved this problem of xml comparison using XSLT 1.0 which can be used for comparing large xml files using an unordered tree comparison algorithm. https://github.com/sflynn1812/xslt-diff-turbo

How would you compare two XML Documents?

13 Answers