TagBites.Expressions

Converts C# text expressions into LINQ expressions using Roslyn, supporting complete language syntax.

Example

public void BasicUseTest()
{
    var expression = "new [] { 1, 2, 3 }.Select(x => (x, x + 1).Item2).Sum()";
    var func = ExpressionParser.Parse(expression, null).Compile();

    Assert.Equal(9, func.DynamicInvoke());
}

public void SimpleTest()
{
    var func = Parse("(a + b) / (double)b");
    Assert.Equal(2.5d, func(3, 2));

    func = Parse("a switch { 1 => b, 2 => b * 2, _ => b + a }");
    Assert.Equal(2, func(1, 2));
    Assert.Equal(4, func(2, 2));
    Assert.Equal(5, func(3, 2));

    static Func<int, int, double> Parse(string expression)
    {
        var options = new ExpressionParserOptions
        {
            Parameters =
            {
                (typeof(int), "a"),
                (typeof(int), "b")
            },
            ResultCastType = typeof(double)
        };
        var lambda = ExpressionParser.Parse(expression, options);
        return (Func<int, int, double>)lambda.Compile();
    }
}

public void TypeTest()
{
    var m = new TestModel { X = 1, Y = 2 };

    var func = Parse("X + Y");
    Assert.Equal(3, func(m));

    func = Parse("X + Nested.X");
    Assert.Equal(3, func(m));

    func = Parse("X + new TestModel { X = 1, Y = 2 }.Y");
    Assert.Equal(3, func(m));

    func = Parse("X + (X == 1 ? Nested.X : Nested.Y)");
    Assert.Equal(3, func(m));
    Assert.Equal(7, func(new TestModel { X = 2, Y = 3 }));

    static Func<TestModel, int> Parse(string expression)
    {
        var options = new ExpressionParserOptions
        {
            Parameters =
            {
                (typeof(TestModel), "this")
            },
            UseFirstParameterAsThis = true,
            ResultType = typeof(int)
        };
        var lambda = ExpressionParser.Parse(expression, options);
        return (Func<TestModel, int>)lambda.Compile();
    }
}

private class TestModel
{
    private TestModel? _nested;

    public int X { get; set; }
    public int Y { get; set; }
    public TestModel Nested => _nested ??= new TestModel { X = Y, Y = X + Y };
}