动态Func键<&IQueryable的LT; TEntity>中IOrderedQueryable< TEntity>>表达 [英] Dynamic Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> Expression
问题描述
的 http://www.asp.net/mvc/tutorials/getting-started-with-ef-使用-MVC /实施的非存储库和-单位按工作模式,在一个-ASP净MVC应用程序
而且我在使用以下方法来查询EF
And i am using method below to query EF
public virtual IEnumerable<TEntity> Get(
Expression<Func<TEntity, bool>> filter = null,
Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
string includeProperties = "")
{
IQueryable<TEntity> query = dbSet;
if (filter != null)
{
query = query.Where(filter);
}
foreach (var includeProperty in includeProperties.Split
(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
{
query = query.Include(includeProperty);
}
if (orderBy != null)
{
return orderBy(query).ToList();
}
else
{
return query.ToList();
}
}
现在我想创建动态函数功能:LT; IQueryable的< TEntity>中IOrderedQueryable< TEntity>>
表达订购我的数据。
Now i want to create dynamic Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>>
expression to order my data.
我只知道字段名的字符串和订单类型(上升,下降)作为字符串(ASC,DESC)
I know only field name as string and order type (ascending, descending) as string (asc, desc)
推荐答案
终于我可以写我想要的方式
finally i could write the method i want.
public static Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> GetOrderBy(string orderColumn, string orderType) {
Type typeQueryable = typeof(IQueryable<TEntity>);
ParameterExpression argQueryable = Expression.Parameter(typeQueryable, "p");
var outerExpression = Expression.Lambda(argQueryable, argQueryable);
string[] props = orderColumn.Split('.');
IQueryable<TEntity> query = new List<TEntity>().AsQueryable<TEntity>();
Type type = typeof(TEntity);
ParameterExpression arg = Expression.Parameter(type, "x");
Expression expr = arg;
foreach(string prop in props) {
PropertyInfo pi = type.GetProperty(prop, BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);
expr = Expression.Property(expr, pi);
type = pi.PropertyType;
}
LambdaExpression lambda = Expression.Lambda(expr, arg);
string methodName = orderType == "asc" ? "OrderBy" : "OrderByDescending";
MethodCallExpression resultExp =
Expression.Call(typeof(Queryable), methodName, new Type[] { typeof(TEntity), type }, outerExpression.Body, Expression.Quote(lambda));
var finalLambda = Expression.Lambda(resultExp, argQueryable);
return (Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>>)finalLambda.Compile();
}
这方法有两个参数,第一个字段名称另一个是递增或递减。方法
结果可以直接与IQueryable的对象使用。
This method takes two parameters, first one field name other one is asc or desc. Result of method can be used directly with IQueryable object.
感谢您的帮助。
这篇关于动态Func键<&IQueryable的LT; TEntity>中IOrderedQueryable< TEntity>>表达的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!