ReHackt.Linq 1.0.0-alpha.14

ReHackt.Linq

Some useful System.Linq.IQueryable extensions such as filtering, ordering, paging...

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QueryableFilter

QueryableFilter<T> allows to dynamically filter an IQueryable<T> with a query string. For example, this can be useful for an API whose clients can filter a collection of entities on any of its properties, or create complex logical queries.

For example

string query = @"Name eq ""Bond"" and (""james"" in Email or (Status in [1, 2] and ""007"" in Codes)) and (Amount lt 1000 or IsEnabled eq false)";

if(QueryableFilter.TryParse(query, out QueryableFilter<Agent> filter) {
    IQueryable<Agent> agents = _agentManager.Agents.Filter(filter);
}
else { /* Handle invalid query */ };

Is equivalent to

IQueryable<Agent> agents = _agentManager.Agents
    .Where(u => u.Name == "Bond"
        && (u.Email.Contains("james")
            || (new int[] { 1, 2 }.Contains(Status) && u.Codes.Contains("007")))
        && (u.Amount < 1000 || u.IsEnabled == false);

Supported in query

• Boolean operators: and, or
• Comparison operators: eq, gt, gte, lt, lte, in (string.Contains or IList.Contains)
• Value types: bool?, DateTimeOffset?, double?, int?, enum, null, string, DateTimeOffset?[], double?[], int?[], string[]
• Parentheses
• Property names (nested properties and collection properties supported)

Not yet supported (planned)

• Boolean operators: not

IQueryable extensions

Filtering

Filter

Filter allows to apply a QueryableFilter<T> to the input sequence using LINQ method syntax.

source.Filter(filter) // filter is a QueryableFilter<T>

Is syntactic sugar for

filter.Apply(source)

This method also allows you to directly filter the input sequence with a query string (implicitly creating a QueryableFilter<T>). Be careful, this can throw an argument exception if the query string is not valid.

source.Filter(filterQuery) // filterQuery is a string

Is syntactic sugar for

QueryableFilter.TryParse(filterQuery, out QueryableFilter<T> filter) ?
    source.Filter(filter) :
    throw new ArgumentException("Invalid filter query", nameof(filterQuery))

WhereIf

source.WhereIf(condition, predicate)

Is syntactic sugar for

condition ? source.Where(predicate) : source

This allows you to keep the LINQ method syntax to apply filters according to a condition that does not depend on the element being tested.

For example

return source
            .Join(...)
            .Where(...)
            .WhereIf(condition1, predicate1)
            .WhereIf(condition2, predicate2)
            .OrderBy(...)
            .Select(...);

Is equivalent to

source = source            
            .Join(...)
            .Where(...);

if(condition1) {
    source = source.Where(predicate1);
} 

if(condition2) {
    source = source.Where(predicate2);
}

return source
            .OrderBy(...)
            .Select(...);

Ordering

OrderBy, OrderByDescending, ThenBy, ThenByDescending

These methods allow you to sort dynamically an input sequence according to a property from each element whose name is taken as a string. OrderBy and OrderByDescending can take a variable number of arguments in order to sort the sequence according to several properties in the order of the arguments.

For example

source.OrderBy("Score", "Year", "Title")

Is equivalent to

source
    .OrderBy(x => x.Score)
    .ThenBy(x => x.Year)
    .ThenBy(x => x.Title)

Paging

PageBy

source.PageBy(page, pageSize)

Is syntactic sugar for

source.Skip(((page < 1 ? 1 : page) - 1) * pageSize).Take(pageSize)