Invoking an expression in a Select expression - LINQ to Entity Framework

Question

I'm trying to use the existing Building Expression class that I made when I tried to make a select clause, but I'm not sure how to attach the expression to the expression tree for Select, I tried to do the following

var catalogs = matchingCatalogs.Select(c => new
                {
                    c.CatalogID,
                    Name = EntitiesExpressionHelper.MakeTranslationExpression<Catalog>("Name", ApplicationContext.Instance.CurrentLanguageID).Compile().Invoke(c),
                    CategoryName = EntitiesExpressionHelper.MakeTranslationExpression<Category>("Name", ApplicationContext.Instance.CurrentLanguageID).Compile().Invoke(c.Category),
                    c.CategoryID,
                    c.StartDateUTC,
                    c.EndDateUTC
                });

But I obviously get the message that the Entity Framework cannot map Invoke to the SQL method. Is there any way around this?

FYI, EntitiesExpressionHelper.MakeTranslationExpression <T> (string name, int languageID) is equivalent to:

x => x.Translations.Count(t => t.LanguageID == languageID) == 0 ? x.Translations.Count() > 0 ? x.Translations.FirstOrDefault().Name : "" : x.Translations.FirstOrDefault(t => t.LanguageID == languageID).Name

EDIT: I understand that I need to use ExpressionVisitor for this, but I'm not sure how to use ExpressionVisitor to change the MemberInitExpression expression, so if anyone knows how to do this, let me know.

Answer 1

vars. . , :

Expression<Func<Foo, Bar>> exp = GenExpression();
var q = matchingCatalogs.Select(exp);

:

var q = matchingCatalogs.Select(GenExpression());

GenExpression L2E. GenExpression L2E, .

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