GitHub - rameel/ramstack.expressionparser: A flexible expression parser library for .NET, allowing dynamic evaluation and binding of expressions with context-aware support.

Ramstack.ExpressionParser is a flexible expression parser library for .NET, allowing dynamic evaluation and binding of expressions with context-aware support.

Getting Started

To install the Ramstack.ExpressionParser NuGet package to your project, run the following command:

dotnet add package Ramstack.ExpressionParser

Usage

var result = ExpressionParser.Parse("math.min(2 + 3, 2 * 3)");
if (result.Success)
{
    var lambda = Expression.Lambda<Func<int>>(result.Value);
    var fn = lambda.Compile();

    Console.WriteLine(fn());
}

Using ContextAwareBinder

ContextAwareBinder allows binding expressions to a specific context, making it possible to reference its properties, fields, and methods directly within expressions.

• The provided context acts as an implicit this, meaning you can access its members without prefixes.
• Case-insensitive binding: identifiers in expressions are resolved in case-insensitive manner (e.g., level, Level, and LEVEL are treated the same).

var parameter = Expression.Parameter(typeof(LogEvent), "logEvent");
var binder = new ContextAwareBinder(parameter);

var result = ExpressionParser.Parse("level == LogLevel.Error && string.IsNullOrEmpty(source)", binder);
var predicate = Expression
    .Lambda<Predicate<LogEvent>>(result.Value, parameter)
    .Compile();

Here, IsEnabled evaluates the parsed expression against a LogEvent instance:

public bool IsEnabled(LogEvent logEvent)
{
    return _predicate(logEvent);
}

This makes it easy to create dynamic, human-readable expressions for filtering or evaluating objects at runtime.

Supported Versions

Contributions

Bug reports and contributions are welcome.

License

This package is released under the MIT License. See the LICENSE file for details.