Meziantou.Framework

Introduction

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Meziantou.Framework.SimpleQueryLanguage parses the queries people type in a search box, such as is:open author:alice comments>=2 crash, and turns them into a filter. You decide what each key means: the library parses the query, the values and the dates, and combines your handlers with AND, OR and NOT.

What you can do with it

  • Filter objects in memory with QueryBuilder<T>: a query becomes a predicate you evaluate on each object. See In-memory queries.
  • Filter database queries with ExpressionQueryBuilder<T>: a query becomes an expression tree that Entity Framework Core, or another LINQ provider, translates to SQL. See Database queries.
  • Give users a familiar syntax: free text, key-value terms, comparisons, ranges, AND, OR, NOT, - and parentheses. See Query syntax.
  • Search by dates with created:this_week or created>=@today-2w. See Values and dates.
  • Accept any input: a malformed query is never an error, and a query too complex to evaluate is reported with a dedicated exception. See Queries from users.

How it works

You register a handler for each key, such as author or created, and optionally a handler for free text. Build parses the query once and returns an object you reuse:

BuilderHandlersResultUse it with
QueryBuilder<T>DelegatesQuery<T>, with Evaluate(T)Objects in memory.
ExpressionQueryBuilder<T>ExpressionsExpressionQuery<T>, with Apply(IQueryable<T>)Entity Framework Core and other IQueryable<T>.

Both builders read the same syntax.

Namespace

The builders and the queries are in the Meziantou.Framework.SimpleQueryLanguage namespace. RangeSyntax<T>, the value of a range handler, is in Meziantou.Framework.SimpleQueryLanguage.Ranges.

Next steps