How to parse OData $filter with regular expression in C#?

c#, odata, regex

Solution

In .NET, there's a library available that will do this for you. Writing your own regex runs the risk of missing some edge case.

Using NuGet, bring in Microsoft.Data.OData. Then, you can do:

using Microsoft.Data.OData.Query;

var result = ODataUriParser.ParseFilter(
  "name eq 'Facebook' or name eq 'Twitter' and subscribers gt 30",
  model,
  type);

`result` here will be in the form of an AST representing the filter clause.

(To get the `model` and `type` inputs, you could parse your $metadata file using something like this:

using Microsoft.Data.Edm;
using Microsoft.Data.Edm.Csdl;

IEdmModel model = EdmxReader.Parse(new XmlTextReader(/*stream of your $metadata file*/));
IEdmEntityType type = model.FindType("organisation");

)

Problem

Hi I'm wondering what the best approach would be to parse an OData $filter string in C#, for example /API/organisations?$filter="name eq 'Facebook' or name eq 'Twitter' and subscribers gt '30'" Should return all organisations with a name of Facebook or Twitter and who have more than 30 subscribers. I've researched quite a bit but can't find any solutions which don't revolve around WCF. I was thinking of using Regex and grouping them so I have a list of Filter classes such that: ``` Filter Resource: Name Operator: Eq Value: Facebook Filter Resource: Name Operator: Eq Value: Twitter Filter Resource: Subscribers Operator: gt Value: 30 ``` but I'm stumped as how to handle ANDs / ORs.

Original source