擴展lambda表達式

Question

我已經將其像創建的現有λ-表達：

Expression<Func<Entities.Area, bool>> where = (x => (x.Created > this.Value || (x.Changed != null && x.Changed > this.Value))); 

現在，我必須與這一個延伸此表達式：

Expression<Func<Entities.Area, bool>> whereAdd = (x => x.Client.Id == ClientInfo.CurrentClient.Id); 

結果應該是這樣的：

Expression<Func<Entities.Area, bool>> where = (x => (x.Created > this.Value || (x.Changed != null && x.Changed > this.Value)) && x.Client.Id == ClientInfo.CurrentClient.Id); 

我不能直接更改第一個表達式的創建，因爲它不是我的代碼。

我希望有人能幫助我如何擴展第一個lambda表達式。

Answer 1

只需創建一個新的AndAlso表達同時服用你的表情的屍體，並作出新的lambda表達式出來的是：

ParameterExpression param = Expression.Parameter(typeof(Entities.Area), "x"); 
Expression body = Expression.AndAlso(where.Body, whereAdd.Body); 

var newWhere = Expression.Lambda<Func<Entities.Area, bool>>(body, param); 

Console.WriteLine(newWhere.ToString()); 
// x => (((x.Created > Convert(value(UserQuery).Value)) OrElse ((x.Changed != null) AndAlso (x.Changed > Convert(value(UserQuery).Value)))) AndAlso (x.Client.Id == ClientInfo.CurrentClient.Id)) 

Answer 2

Combining two expressions (Expression<Func<T, bool>>)

var body = Expression.AndAlso(where.Body, whereadd.Body); 
var lambda = Expression.Lambda<Func<Entities.Area,bool>>(body, where.Parameters[0]);