C# Expression Parser

The project provides a simple expression parser that transforms a string into a valid C# expression representing a function. The function can be called with or without a parameter or as part of a LINQ query.

Getting Started

The library contains a static class with 4 methods for parsing:

Func<TOutput> Parse<TOutput>(string input)
Delegate Parse(string input)
Func<TInput, TOutput> ParseFor<TInput, TOutput>(string input)
Delegate ParseFor<TInput>(string input)

And 3 methods used to give support to external types:

IExpressionParser Using(Type type, string alias = null)
IExpressionParser Using(IEnumerable<Type> types)
IExpressionParser Using(IDictionary<Type, string> typeMap)

All methods are also exposed by the public interface IExpressionParser.

Prerequisites

There is no prerequisite to install and use the methods included in this library.

Installing

You can install the ExpressionParser by downloading it as a NuGet package:

Install-Package CSharp.ExpressionParser

After that, you can just use the call directly from your code. Here is a couple of usage examples:

var result1 = ExpressionParser.Parse<int>("(3 + 2) * 3")(); //result1 should be an integer of value 15
var result2 = ExpressionParser.ParseFor<SomeClass, bool>("Id == 23 && IsActive == true")(instance);  //result2 should be a boolean that the value shoul depend on the instance provided as input

If you don't know the output of the result in advance you can use:

var expression = ExpressionParser.Parse(someStringToBeParsed); //expression will have a delegate returning an object.
var result = expression.DynamicInvoke();  //result will have the result of the expression as an object.

Here are a few samples of expressions that will be accepted by the case above:

"2.0 / 5.0" ==> Expected result: 0.4 (decimal)
"3 + 2 * 3" ==> Expected result: 9 (int)
"1 >= 1" ==> Expected result: true (bool)

This is also supported when an input value is provided, but in this case, the type of the input has to be informed. Here is an example:

var expression = ExpressionParser.ParseFor<SomeClass>(someStringToBeParsed);
var result = expression.DynamicInvoke(instaceOfTypeSomeClass);

In order to support external types or interfaces you can use the Using method to add them. For example:

var result = ExpressionParser.Using(new { typeof(IPerson), type(IMovie) }).Parse<bool>("((IPerson)record.Person).Age > ((IMovie)record.Movie).AgeLimit")(record);

More examples can be found in the test project.

Supported Operators and Types

Here is a list of supported operators.

The Tests

A NUnit 3 test project is provided in the solution.
The tests currently provide 100% of code coverage, but they are not complete.
We plan to include more positive test cases and many more negative test cases in the future commits.

Contributing

Please read CONTRIBUTING for details on our code of conduct, and the process for submitting pull requests to us.

Versioning

We use SemVer for versioning. For the versions available, see the tags on this repository.

Authors

• Andre Vianna - Initial work - AndreVianna

See also the list of contributors who participated in this project.

License

This project is licensed under the MIT License - see the LICENSE.md file for details