我正在为任何列/字段映射的查询中的 searchText 寻找通用过滤器
public static IQueryable<T> Filter<T>(this IQueryable<T> source, string searchTerm)
{
var propNames = typeof(T).GetProperties(BindingFlags.Instance | BindingFlags.Public).Where(e=>e.PropertyType == typeof(String)).Select(x => x.Name).ToArray();
//I am getting the property names but How can I create Expression for
source.Where(Expression)
}
这里我给大家举个例子
现在从我在 Asp.net MVC4 中的 HTML5 表中,我提供了一个搜索框来过滤输入文本的结果,它可以匹配以下任何列/菜单类属性值,我想在服务器中进行此搜索side ,我该如何实现它。
EF 模型类
public partial class Menu
{
public int Id { get; set; }
public string MenuText { get; set; }
public string ActionName { get; set; }
public string ControllerName { get; set; }
public string Icon { get; set; }
public string ToolTip { get; set; }
public int RoleId { get; set; }
public virtual Role Role { get; set; }
}
最佳答案
您可以使用表达式:
private static Expression<Func<T, bool>> GetColumnEquality<T>(string property, string term)
{
var obj = Expression.Parameter(typeof(T), "obj");
var objProperty = Expression.PropertyOrField(obj, property);
var objEquality = Expression.Equal(objProperty, Expression.Constant(term));
var lambda = Expression.Lambda<Func<T, bool>>(objEquality, obj);
return lambda;
}
public static IQueryable<T> Filter<T>(IQueryable<T> source, string searchTerm)
{
var propNames = typeof(T).GetProperties(BindingFlags.Instance | BindingFlags.Public)
.Where(e => e.PropertyType == typeof(string))
.Select(x => x.Name).ToList();
var predicate = PredicateBuilder.False<T>();
foreach(var name in propNames)
{
predicate = predicate.Or(GetColumnEquality<T>(name, searchTerm));
}
return source.Where(predicate);
}
结合名字PredicateBuilder
来自 C# 的 NutShell。这也是 LinqKit 的一部分.
例子:
public class Foo
{
public string Bar { get; set; }
public string Qux { get; set; }
}
Filter<Foo>(Enumerable.Empty<Foo>().AsQueryable(), "Hello");
// Expression Generated by Predicate Builder
// f => ((False OrElse Invoke(obj => (obj.Bar == "Hello"), f)) OrElse Invoke(obj => (obj.Qux == "Hello"), f))
关于c# - Linq IQueryable 通用筛选器,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17832989/