TurboYang.Dynamic.Expression

The library for compile and evaluate custom expressions. Implementation for .NET Standard 2.0.

Installation

Install with Package Manager:

Install-Package TurboYang.Dynamic.Expression

Usage: A simple expression

String expression = @"(1 + 2) * 3 / 3;";

ExpressionCompiler compiler = new ExpressionCompiler();
ExpressionContext context = new ExpressionContext();

Decimal result = compiler.Evaluate<Decimal>(expression, context);      // result == 3

Usage: Expression with parameters

String expression = @"(x + y) * z;";

ExpressionCompiler compiler = new ExpressionCompiler();
ExpressionContext context = new ExpressionContext();

context.Bind("x", 1);
context.Bind("y", 2);
context.Bind("z", 3);

Int32 result = compiler.Evaluate<Int32>(expression, context);      // result == 9

You can also bind parameters through anonymous class.

String expression = @"(x + y) * z;";

ExpressionCompiler compiler = new ExpressionCompiler();
ExpressionContext context = new ExpressionContext(new 
{
    x = 1,
    y = 2,
    z = 3
});

Int32 result = compiler.Evaluate<Int32>(expression, context);      // result == 9

Usage: Function expression

String expression = @"Pow(2, 3);";

ExpressionCompiler compiler = new ExpressionCompiler();
ExpressionContext context = new ExpressionContext();

Decimal result = compiler.Evaluate<Decimal>(expression, context);      // result == 8

Usage: Constant expression

String expression = @"PI * Pow(r, 2);";

ExpressionCompiler compiler = new ExpressionCompiler();
ExpressionContext context = new ExpressionContext(new 
{
    r = 10;
});

Decimal result = compiler.Evaluate<Decimal>(expression, context);      // result == 314.159265358979

Usage: Intervening variable

String expression = @"x = a + b; y = c + d; x * y";

ExpressionCompiler compiler = new ExpressionCompiler();
ExpressionContext context = new ExpressionContext(new 
{
    a = 1,
    b = 2,
    c = 3,
    d = 4
});

Int32 result = compiler.Evaluate<Int32>(expression, context);      // result == 21

You can call ExpressionContext.Lookup Method to get the intervening variable value.

Int32 x = context.Lookup<Int32>("x");         // 3
Int32 y = context.Lookup<Int32>("y");         // 7

Usage: Custom function

You can customize your functions, such as defining a function(Circumference) to calculate the circumference of a circle.

public class CircumferenceExpression : FunctionExpression
{
    public override Int32 ParameterCount => 1;

    protected override String Name => "Circumference";

    public override Object Evaluate(ExpressionContext context)
    {
        // Please do not remove this code
        base.Evaluate(context);

        return 2 * (Decimal)Math.PI * OperandValues[0];
    }
}

Then register and evaluate your function expression.

String expression = @"Circumference(r)";

ExpressionCompiler compiler = new ExpressionCompiler();
compiler.RegisterExpression(typeof(CircumferenceExpression));

ExpressionContext context = new ExpressionContext(new
{
    r = 1
});

Decimal result = compiler.Evaluate<Decimal>(expression, context);      // result == 6.28318530717958

Built in expression

Expression	Symbol	Example
Addition	+	x + y
Subtraction	-	x - y
Multiply	*	x * y
Division	/	x / y
Modulus	%	x % y
Left Shift	<<	x << y
Right Shift	>>	x >> y
Left Parenthese	(	(x + y) * z
Right Parenthese	)	(x + y) * z
Bitwise And	&	x & y
Bitwise Or	|	x | y
Exclusive Or	^	x ^ y
And	&&	x && y
Or	||	x || y
Break	;	x + y;
Comma	,	Pow(x, y)
True	true	x == true
False	false	x == false
Equality	==	x == y
Inequality	!=	x != y
Less Than	<	x < y
Less Than Or Equal	<=	x <= y
Greater Than	>	x > y
Greater Than Or Equal	>=	x >= y
Pow	Pow()	Pow(x, y)
Numeric		3.14
String		"Hello world!"
Variable		x
PI Ratio	PI	PI
Euler's Number	E	E