NCalc

This is the Tech Software fork of NCalc. It exists to allow callers to opt-in to pre-v5.1 handling of the + operator as meaning string concatenation if the left-hand value is a string.

NCalc is a fast and lightweight expression evaluator library for .NET, designed for flexibility and high performance. It supports a wide range of mathematical and logical operations. NCalc can parse any expression and evaluate the result, including static or dynamic parameters and custom functions. NCalc targets .NET 8, .NET Standard 2.0 and NET Framework 4.8.

Docs

Need help or want to learn more? Check the team's docs.

Learn more

For additional information on the technique we used to create this framework please read this article.

Help

Important

If you need help, please open an issue and include the expression to help us better understand the problem. Providing this information will aid in resolving the issue effectively.

Getting Started

If you want to evaluate simple expressions:

dotnet add package NCalcSync 

Want async support at your functions and parameters?

dotnet add package NCalcAsync 

Dependency Injection? We got you covered:

dotnet add package NCalc.DependencyInjection

Functionalities

Simple Expressions

var expression = new Expression("2 + 3 * 5");
Debug.Assert(17 == expression.Evaluate());

Evaluates .NET data types

Debug.Assert(123456 == new Expression("123456").Evaluate()); // integers
Debug.Assert(new DateTime(2001, 01, 01) == new Expression("#01/01/2001#").Evaluate()); // date and times
Debug.Assert(123.456 == new Expression("123.456").Evaluate()); // floating point numbers
Debug.Assert(true == new Expression("true").Evaluate()); // booleans
Debug.Assert("azerty" == new Expression("'azerty'").Evaluate()); // strings

Handles mathematical functional from System.Math

Debug.Assert(0 == new Expression("Sin(0)").Evaluate());
Debug.Assert(2 == new Expression("Sqrt(4)").Evaluate());
Debug.Assert(0 == new Expression("Tan(0)").Evaluate());

Evaluates custom functions

var expression = new Expression("SecretOperation(3, 6)");
expression.Functions["SecretOperation"] = (args) => {
    return (int)args[0].Evaluate() + (int)args[1].Evaluate();
};

Debug.Assert(9 == expression.Evaluate());

Handles unicode characters

Debug.Assert("経済協力開発機構" == new Expression("'経済協力開発機構'").Evaluate());
Debug.Assert("Hello" == new Expression(@"'\u0048\u0065\u006C\u006C\u006F'").Evaluate());
Debug.Assert("だ" == new Expression(@"'\u3060'").Evaluate());
Debug.Assert("\u0100" == new Expression(@"'\u0100'").Evaluate());

Define parameters, even dynamic or expressions

var expression = new Expression("Round(Pow([Pi], 2) + Pow([Pi2], 2) + [X], 2)");

expression.Parameters["Pi2"] = new Expression("Pi * [Pi]");
expression.Parameters["X"] = 10;

expression.DynamicParameters["Pi"] = _ => {
    Console.WriteLine("I'm evaluating π!");
    return 3.14;
};

Debug.Assert(117.07 == expression.Evaluate());

Caching and Serializing

This example uses Newtonsoft.Json.

Serializing

var parsedExpression = LogicalExpressionFactory.Create(expression, ExpressionOptions.NoCache);
var serialized = JsonConvert.SerializeObject(parsedExpression, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.All // We need this to allow serializing abstract classes
});

Deserializing

var deserialized = JsonConvert.DeserializeObject<LogicalExpression>(serialized, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.All
});

Expression.CacheEnabled = false; // We cannot use NCalc's built in cache at the same time.

var expression = new Expression(deserialized);
expression.Parameters = new Dictionary<string, object> {
    {"waterlevel", inputValue}
};

var result = expression.Evaluate();

You can also use our Memory Cache plugin.

Lambda Expressions

var expression = new Expression("1 + 2");
Func<int> function = expression.ToLambda<int>();
Debug.Assert(function()); //3

Related projects

Parlot

Fast and lightweight parser creation tools by Sébastien Ros that NCalc uses at its parser.

PanoramicData.NCalcExtensions

Extension functions for NCalc to handle many general functions,
including string functions, switch, if, in, typeOf, cast etc.
Developed by David, Dan and all at Panoramic Data.

Jint

JavaScript Interpreter for .NET by Sébastien Ros, the author of NCalc library.
Runs on any modern .NET platform as it supports .NET Standard 2.0 and .NET 4.6.1 targets (and up).

NCalcJS

A TypeScript/JavaScript port of NCalc.

NCalc101

NCalc 101 is a simple web application that allows you to try out the NCalc expression evaluator, developed by Panoramic Data.

JJMasterData

JJMasterData is a runtime form generator from database metadata. It uses NCalc to evaluate expressions used in field visibility and other dynamic behaviors.

NCalc versioning

The project uses Nerdbank.GitVersioning tool to manage versions.
Each library build can be traced back to the original git commit.

Preparing and publishing a new release

1. Make sure that nbgv dotnet CLI tool is installed and is up-to-date
2. Run nbgv prepare-release to create a stable branch for the upcoming release, i.e. release/v1.0
3. Switch to the release branch: git checkout release/v1.0
4. Execute unit tests, update the README, release notes in csproj file, etc. Commit and push your changes.
5. Run dotnet pack -c Release and check that it builds Nuget packages with the right version number.
6. Run nbgv tag release/v1.0 to tag the last commit on the release branch with your current version number, i.e. v1.0.7.
7. Push tags as suggested by nbgv tool: git push origin v1.0.7
8. Go to GitHub project page and create a release out of the last tag v1.0.7.
9. Verify that github workflow for publishing the nuget package has completed.
10. Switch back to master and merge the release branch.

Discord Server

If you want to talk with us, get support or just get the latest NCalc news, come to our discord server.