如何修改這個擴展方法接受兩個字符串參數？

Question

我有一個功能類似一個SQL IN以下擴展方法：

public static IQueryable<TEntity> WhereIn<TEntity, TValue> 
    (
    this ObjectQuery<TEntity> query, 
    Expression<Func<TEntity, TValue>> selector, 
    IEnumerable<TValue> collection 
) 
    { 
     if (selector == null) throw new ArgumentNullException("selector"); 
     if (collection == null) throw new ArgumentNullException("collection"); 
     if (!collection.Any()) 
      return query.Where(t => false); 

     ParameterExpression p = selector.Parameters.Single(); 

     IEnumerable<Expression> equals = collection.Select(value => 
      (Expression)Expression.Equal(selector.Body, 
       Expression.Constant(value, typeof(TValue)))); 

     Expression body = equals.Aggregate((accumulate, equal) => 
      Expression.Or(accumulate, equal)); 

     return query.Where(Expression.Lambda<Func<TEntity, bool>>(body, p)); 
    } 



     //Optional - to allow static collection: 
     public static IQueryable<TEntity> WhereIn<TEntity, TValue> 
      (
      this ObjectQuery<TEntity> query, 
      Expression<Func<TEntity, TValue>> selector, 
      params TValue[] collection 
     ) 
     { 
      return WhereIn(query, selector, (IEnumerable<TValue>)collection); 
     } 

的問題是，當我這樣稱呼它：

predicate = predicate.And(x => WhereIn(x.id, Ids)); 

它給了我一個錯誤：The type arguments for method 'WhereIn<TEntity,TValue>(System.Data.Objects.ObjectQuery<TEntity>, System.Linq.Expressions.Expression<System.Func<TEntity,TValue>>, params TValue[])' cannot be inferred from the usage. Try specifying the type arguments explictly.

x.id is a Ids are both of type string.

我其實並不想改變方法signaure，我就拉澤r改變了對它的呼籲，但我不確定在WhereIn<>的括號之間應該放入什麼。

Answer 1

我想你調用擴展方法是錯誤的。

嘗試這樣的：

predicate = predicate.And(x => x.WhereIn(x.id, Ids));