McRule/README.md

McRule

Rule based filtering using expression trees.

Predicate Grammar

Predicates are built using simple syntax to select comparison operators and methods for the specified properties on a supplied object of a specified type. That is the policy specifies the type by name, property to match against and the value the property must have. A simple equality comparison is used by default but operators can be prefixed to a policy operand for customized behavior, as shown below.

Property Type	Operator	Comparison Description
string	*	Astrisk can appear at the beginning, end or both denoting: StartsWith, EndsWith or Contains respectively.
string	~	Denotes case-insensitive comparison when used in .net, things that translate the resulting expression tree may not respect this. EF core for instance won't bind a Contains with case insensitive comparison from the string methods at all, results in a runtime error. Note: when used with wildcard, tilde operator must be first: '~*foo'.
string	!	Negative expression. Must prefix all other operators.
IComparable	>	Greater-than comparison.
IComparable	>=	Greater-than or equal to comparison.
IComparable	<	Less-than comparison.
IComparable	<=	Less-than or equal to comparison.
IComparable	<>, !=, !	Not-equal to comparison.

Note: the IComparable interface is mostly used for numerical types but custom types with comparison providers may work at runtime.

Literal Values

Literal values, as needed, use handlbar syntax: {{ value }}. Null checks are implicitly added to most expressions but sometimes you need an expression that evaluates true for null values. In that case, a null literal is represented as {{null}}. Case sensitivity doesn't matter, nor does internal whitespace inside the braces. Values are interpretted like so:

var matched = handlebarPattern.Match(value);
if (matched.Success) {
    switch (matched.Groups.FirstOrDefault(x => x.Name == "literal")?.Value?.Trim()?.ToLower()) {
        case "null":
            return (true, new NullValue());
            break;
    }
}

Examples

Notes

Publish nuget package:

dotnet nuget push McRule.0.0.5.nupkg --api-key <api key> --source https://api.nuget.org/v3/index.json