Umamimolecule.ConditionParser 0.1.1

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Condition Parser

A rules engine for .Net to evaluate multiple combinations of conditions.

new ConditionParser().Parse("'Quick brown fox' Contains 'fox'");    // true
new ConditionParser().Parse("123.456 > 200 and 123.456 <= 300");    // false
new ConditionParser().Parse("'Hot coffee' MatchesRegex '^Hot'");    // true

Installation

Install the ConditionParser NuGet package in Visual Studio.

PM> Install-Package Umamimolecule.ConditionParser

Quick start

using System;
using Umamimolecule;

namespace ConditionParserExample
{
    public static class Program
    {
        public static void Main()
        {
            // A simple example to check if a number is > 10.5 and <= 100
            Console.WriteLine("Enter a number: ");
            string number = Console.ReadLine();
            var input = $"{number} > 10.5 and {number} <= 100";
            var result = new ConditionParser().Parse(input);
            Console.WriteLine($"{input} = {result}");
        }
    }
}

Options

The parser behaviour can be controlled by passing in options in the constructor.

using System;
using System.Text.RegularExpressions;

var parser = new ConditionParser(
    new ConditionParserOptions()
    {
        // Behaviour for regex operations
        // Default = RegexOptions.IgnoreCase
        RegexOptions = RegexOptions.IgnoreCase | RegexOptions.RightToLeft,
        
        // Behaviour for string comparison operations
        // Default = StringComparison.OrdinalIgnoreCase
        StringComparison = StringComparison.CurrentCulture
    });

Operators

The following operators are available:

^1.Applies to all data types except for boolean.

^2.Applies to boolean types only.

Data types

The following data types are supported:

• Null
• Boolean
• Date and date-time
• Integer
• Double
• String

Null

Null values are represented by the keyword null.

Examples:

new ConditionParser().Parse("null == null");    // true
new ConditionParser().Parse("null IsNull");     // true
new ConditionParser().Parse("'abc' == null");   // false

Boolean

Represented by the keywords true and false.

Examples:

new ConditionParser().Parse("true != false");   // true
new ConditionParser().Parse("true IsFalse");    // false

Date and date-time

Date and date-time values are represented by a quoted date value, prefixed with either date or datetime. Single or double-quotes can be used.

Date values are represented in UTC values at midnight. Date and date-time values can be compared against each other.

Examples:

new ConditionParser().Parse("date'2022-12-31' > date'2022-12-01'"); // true
new ConditionParser().Parse("datetime'2022-12-31T01:23:45.678Z' > datetime'2022-12-31T00:00:00.000Z"); // true
new ConditionParser().Parse("date'2022-12-31' == datetime'2022-12-31T00:00:00Z'"); // true

Integer

Integers are represented a sequence of digits, optionally with a leading - to indicate a negative value.

Examples:

new ConditionParser().Parse("1 > 0");       // true
new ConditionParser().Parse("-1 < 0");      // true
new ConditionParser().Parse("1234 == 1");   // false

Double

Doubles are represented by a number with a decimal point, optionally with a leading - to indicate a negative value.

Doubles and integers can be compared against each other.

Examples:

new ConditionParser().Parse("1.23 > 1.1");      // true
new ConditionParser().Parse("-1.23 < 0.0");     // true
new ConditionParser().Parse("1.23 > 1");        // true
new ConditionParser().Parse("1.0 == 1");        // true

String

String values in an expression can be surrounded by either single or double quotes. If the string value contains quotes they need to be escaped as follows:

Order of precedence

Like many other languages such as C#, C and Java, and operators are evaluated before or.

Expressions can be surrounded by parentheses to control order of evaluation.

new ConditionParser().Parse("('ABC' Contains 'B' or 'ABC' Contains 'C') and (202 >= 200 and 202 < 400)");    // true