[英]Linq Expression tree Any() issue
您好,我在使用.Any()擴展方法的表達式樹時遇到麻煩。
這是我的代碼:
IQueryable<Book> querableBooks = Books.Values.AsQueryable<Book>();
ParameterExpression pe = Expression.Parameter(typeof(Book), "book");
MemberExpression props = Expression.Property(pe, "properties");
ParameterExpression propList = Expression.Parameter(typeof(List<BookProperty>), "properties");
var _test = Expression.Lambda<Func<List<BookProperty>, bool>>(operation, new ParameterExpression[] { propList });
var _Any = Expression.Call(typeof(Enumerable), "any", new Type[] { typeof(BookProperty) }, new Expression[] { propList });
Expression Lamba = Expression.Lambda(_Any, _props);
_test返回{屬性=>(((bookProperty.type.key ==“內衣”)和(bookProperty.value ==“ 1”))}}
_Any返回{properties.Any()}
Lambda返回{book.properties => properties.Any()}
Book類是這樣的:
public class Book : IBook
{
public int id { get; set; }
//Removed for clarity
public List<BookProperty> properties { get; set; }
}
BookProperty類:
public class BookProperty
{
public BookProperty()
{
value = "0";
}
public int id { get; set; }
public int bookId { get; set; }
public Book book { get; set; }
public int typeId { get; set; }
public BookPropertyType type { get; set; }
public string value { get; set; }
}
和BookPropertyType類:
public class BookPropertyType
{
public int id { get; set; }
public string groupe { get; set; }
public string key { get; set; }
public string label { get; set; }
public int order { get; set; }
public string editorType { get; set; }
public string unite { get; set; }
}
所以我很接近它,但是我不知道如何正確地合並所有這些以得到這樣的查詢
{book.propertie.Any(bookProperty => bookProperty.type.key ==“內衣”)和(bookProperty.value ==“ 1”)}
謝謝你的幫助。
如果我理解正確,那么您正在尋找這樣的表達方式:
Expression<Func<Book, bool>> bookPredicate = book => book.properties.Any(
bookProperty => bookProperty.type.key == "lingerie" && bookProperty.value == "1");
您可以像這樣動態地構建它:
var book = Expression.Parameter(typeof(Book), "book");
var properties = Expression.PropertyOrField(book, "properties");
var bookProperty = Expression.Parameter(typeof(BookProperty), "bookProperty");
// bookProperty.type.key == "lingerie"
var conditionA = Expression.Equal(
Expression.PropertyOrField(Expression.PropertyOrField(bookProperty, "type"), "key"),
Expression.Constant("lingerie")
);
// bookProperty.value == "1"
var conditionB = Expression.Equal(
Expression.PropertyOrField(bookProperty, "value"),
Expression.Constant("1")
);
// bookProperty.type.key == "lingerie" && bookProperty.value == "1"
var condition = Expression.AndAlso(conditionA, conditionB);
// bookProperty => bookProperty.type.key == "lingerie" && bookProperty.value == "1"
var predicate = Expression.Lambda<Func<BookProperty, bool>>(condition, bookProperty);
// book.properties.Any(bookProperty => bookProperty.type.key == "lingerie" && bookProperty.value == "1")
var anyCall = Expression.Call(
typeof(Enumerable), "Any", new[] { typeof(BookProperty) },
properties, predicate
);
// book => book.properties.Any(...)
var bookPredicate = Expression.Lambda<Func<Book, bool>>(anyCall, book);
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