學習并使用了兩種linq to entity 的實作sql關鍵字in的查詢方法

//構造Lambda語句

       private static Expression<Func<TElement, bool>> BuildWhereInExpression<TElement, TValue>(Expression<Func<TElement, TValue>> propertySelector, IEnumerable<TValue> values)

        {

            ParameterExpression p = propertySelector.Parameters.Single();

            if (!values.Any())

                return e => false;

            var equals = values.Select(value => (Expression)Expression.Equal(propertySelector.Body, Expression.Constant(value, typeof(TValue))));

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

            return Expression.Lambda<Func<TElement, bool>>(body, p);

        }

//調用

      string[] ids = new string[]{"id1","id2","id3"}；

      db.ProjectFiles.Where(BuildWhereInExpression<Profile,int>(v=>v.Id,ids);

//封裝方法

        public static IQueryable<TElement> WhereIn<TElement, TValue>(this IQueryable<TElement> source, Expression<Func<TElement, TValue>> propertySelector, params TValue[] values)

            return source.Where(BuildWhereInExpression(propertySelector, values));

//直接使用下列方法調用

      db.ProjectFiles.WhereIn(c => c.Id,ids);

//字元串構造

//這個方法比較簡單

      cstIds=cstIds.Replace(",","','");

      var query = db.ProjectFiles.Where("it.Id in {'" + cstIds + "'}");