Predicate build with NET Core and EF Core

问题

Very quick question :

I'm trying to create a predicate builder like this :

    var predicate = PredicateBuilder.False<MyObject>();

But seems that is not available in Net Core And EF Core.

Am I missing a package or something ?

回答1:

Are you sure that the PredicateBuilder you were using was not a custom class? A PredicateBuilder is shipped as part of LINQKit but the source is also available here as follows:

public static class PredicateBuilder
{
    public static Expression<Func<T, bool>> True<T>() { return f => true; }

    public static Expression<Func<T, bool>> False<T>() { return f => false; }

    public static Expression<Func<T, bool>> Or<T> (this Expression<Func<T, bool>> expr1,
                                                      Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
        return Expression.Lambda<Func<T, bool>>
          (Expression.OrElse (expr1.Body, invokedExpr), expr1.Parameters);
    }

    public static Expression<Func<T, bool>> And<T> (this Expression<Func<T, bool>> expr1,
                                                       Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
        return Expression.Lambda<Func<T, bool>>
          (Expression.AndAlso (expr1.Body, invokedExpr), expr1.Parameters);
    }
}

来源：https://stackoverflow.com/questions/51720429/predicate-build-with-net-core-and-ef-core