weiran / eflinqexpressionprojection

Build LINQ expression projections that are reusable.

EFLinqExpressionProjecton

This project enables the reuse of LINQ expression logic in projections. This is a fork of LINQ Expression Projection but with support for async queries from Entity Framework 6 and later.

Usage

To use, call extension method AsExpressionProjectable() on the collection queried, and when projecting call the extension method Project<TIn, TResult>(TIn) (on a field, method or any other code element) returning a selector of type Expression<Func<TIn, TResult>>. TIn and TResult can be anything, and they will both be inferred by the compiler meaning that usages of Project() do not have to explicitly specify them.

Example:

Expression<Func<Project, double>> averageEffectiveAreaExpression =
  proj => proj.Subprojects.Average(sp => sp.Area);

var projects = await context.Projects
  .AsExpressionProjectable()
  .Select(p => new 
  {
    Project = p,
    AverageEffectiveArea = averageEffectiveAreaExpression.Project(p)
  })
  .ToListAsync();

Installation

Find this on NuGet: https://www.nuget.org/packages/EFLinqExpressionProjection

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By Weiran Zhang
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