[100分]紧急求助：LinQ下使用IQueryable<T>如何将返回类型<T>使用匿名类型
问题描述如下：
我有一个方法如下：
public IQueryable DissensionList(Guid guid)
{
var p = from d in db.T_民事调解 where (d.社区Guid == guid) select new {序号=d.ID,d.纠纷甲方,d.纠纷乙方,d.调解人,d.调解时间,d.纠纷类别 };
return p;
}
现因为需求改变，需要在返回的IQueryable中使用Linq进行再次查询、筛选，但现在返回的类别为IQueryable，而IQueryable不能使用LinQ查询，
但是IQueryable<T>可以，但是<T>的类型是由方法内部中的
select new {序号=d.ID,d.纠纷甲方,d.纠纷乙方,d.调解人,d.调解时间,d.纠纷类别 };
来确定的，而且这个类型是不确定的，现疑问如下：
如何将这个返回的<T>类型设为匿名类型，由返回类型来自适应生成。
或者提供其它解决方案，返回方法内部生成的匿名类型相对应的List<T>或IQueryable<T>谢谢！
看了你的帖子，经过3天的努力我帮你总结了两个可行的方案，第一个方案比较简单点。第二个比较难
方案一： 利用自建类型
public IEnumerable<dd> get()
{
IEnumerable<dd> re = from n in gj.zuixinZhaosheng
select new dd { id = n.id, jz = n.jianzhang };
return re;
}
//手动创建对象类型
public class dd
{
public int id { get; set; }
public string jz { get; set; }
}
客户代码、
protected void Button1_Click(object sender, EventArgs e)
{
zuixinZhaoshengbll b = zuixinZhaoshengbll.getinstance();
foreach (var item in b.get())
{
Response.Write(item.id.ToString() + "</br>");
Response.Write(item.jz.ToString() + "</br>");
}
}
方案二： 反射方法
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Reflection;
namespace AnonymouseType
{
class AnonymouseSolve
{
//取得ProductID,ProductName，CategoryName
public IEnumerable GetAnonymousResult()
{
NorthwindDataContext db = new NorthwindDataContext();
var result = db.Products.Select(p => new
{
产品ID = p.ProductID,
产品名称 = p.ProductName,
类别名称 = p.Category.CategoryName
});
return result;
}
//取得ProductID,ProductName，CategoryName的前10条记录
public IEnumerable GetTop10Result(IEnumerable _result)
{
var result = _result.Cast<object>();
var set = result.Select(p => new
{ //利用反射取得传入的匿名类型的信息
产品ID = p.GetType().GetProperty("产品ID").GetValue(p, null).ToString(),
产品名称 = p.GetType().GetProperty("产品名称").GetValue(p, null).ToString(),
类别名称 = p.GetType().GetProperty("类别名称").GetValue(p, null).ToString()
}).Take(10);
return set;
}
public IEnumerable GetTop10Result(object IEnumerableOject)
{
var result = (IEnumerable)IEnumerableOject;
return this.GetTop10Result(result);
}
}
}
测试
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Reflection;
namespace AnonymouseType
{
class Program
{
static void Main(string[] args)
{
AnonymouseSolve solve = new AnonymouseSolve();
foreach (var item in solve.GetTop10Result(solve.GetAnonymousResult()))
{
Console.WriteLine("-----------------------------------------");
Type itemType = item.GetType();
Console.WriteLine("产品ID:" + itemType.GetProperty("产品ID").GetValue(item, null));
Console.WriteLine("产品名称:" + itemType.GetProperty("产品名称").GetValue(item, null));
Console.WriteLine("类别名称:" + itemType.GetProperty("类别名称").GetValue(item, null));
Console.WriteLine("-----------------------------------------");
Console.WriteLine();
}
var obj = (object)solve.GetAnonymousResult();
foreach (var item in solve.GetTop10Result(obj))
{
Console.WriteLine("-----------------------------------------");
Type itemType = item.GetType();
Console.WriteLine("产品ID:" + itemType.GetProperty("产品ID").GetValue(item, null));
Console.WriteLine("产品名称:" + itemType.GetProperty("产品名称").GetValue(item, null));
Console.WriteLine("类别名称:" + itemType.GetProperty("类别名称").GetValue(item, null));
Console.WriteLine("-----------------------------------------");
Console.WriteLine();
}
}
}
}
linq返回dynamic类型的匿名实体
这样会报错：
void Main()
{
var x=GetSpareInfoByCode();
Console.Write(x.Key);//报错：“object”未包含“Key”的定义
}
public dynamic GetSpareInfoByCode(){
var words =
from word in "The quick brown fox jumps over the lazy dog".Split()
orderby word.ToUpper()
select word;
var duplicates =
from word in words
group word.ToUpper() by word.ToUpper() into g
where g.Count() > 1
select new { g.Key, Count = g.Count() };
return duplicates;
}
使用tolist
void Main()
{
//var x=GetSpareInfoByCode();
IEnumerable<object> y=GetSpareInfoByCode();
//foreach (var item in (IEnumerable<object>)x)
foreach (var item in y)
{
Console.Write(item.GetType().GetProperty("Key").GetValue(item, null));
Console.Write(item.GetType().GetProperty("Count").GetValue(item, null));
}
}
public dynamic GetSpareInfoByCode(){
var words =
from word in "The quick brown fox jumps over the lazy dog".Split()
orderby word.ToUpper()
select word;
var duplicates =
from word in words
group word.ToUpper() by word.ToUpper() into g
where g.Count() > 1
select new { g.Key, Count = g.Count() };
return duplicates.ToList();
}
有木有更简单高效的方式呢
如何把匿名类型.GetType()返回的对象传进泛型里面
//怎么取得匿名类型的Type放到
//泛型T当中？？
var 匿名 = new {
A = 0,
B = 1 };
Type t = 匿名.GetType();
//然后下面
var xx = dbContext.Database.SqlQuery<t>("sql");
//就悲剧了
var xx2 = dbContext.Database.SqlQuery<dynamic>("sql");
//xx2有列表,但是都是Object..~~~无法显示真实项,用Profile跟..SQL确实提交了.
求解释
msdn大神的解决办法
看到了所以记录下来
出现那个问题的原因是动态类型上没有 Entity Framework 需要的属性定义，Entity Framework 是通过反射类型上的属性来做映射的。为了解决这个问题，我用到了 Emit 技术，动态产生一个类型，并且动态写入 IL 代码产生属性。 代码如下，测试在 C# 4.0 上通过。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Entity;
using System.Collections;
using System.Reflection.Emit;
using System.Reflection;
namespace Demo
{
public class Program
{
public static void Main(string[] args)
{
string connectionString = "Server=(local); Integrated Security=true; Database=master";
using (DbContext context = new DbContext(connectionString))
{
TypeBuilder builder = Program.CreateTypeBuilder("MyDynamicAssembly", "MyModule", "MyType");
Program.CreateAutoImplementedProperty(builder, "name", typeof(string));
Program.CreateAutoImplementedProperty(builder, "type", typeof(string));
Program.CreateAutoImplementedProperty(builder, "id", typeof(int));
Type resultType = builder.CreateType();
dynamic queryResult = context.Database.SqlQuery(resultType, "SELECT * FROM sys.sysobjects");
Console.WriteLine("{0,20} {1,4} {2,10}", "Name", "Type", "ID");
foreach (dynamic item in queryResult)
{
Console.WriteLine("{0,10} {1,4} {2,10}", item.name, item.type, item.id);
}
}
Console.ReadKey();
}
public static TypeBuilder CreateTypeBuilder(string assemblyName, string moduleName, string typeName)
{
TypeBuilder typeBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName(assemblyName), AssemblyBuilderAccess.Run).DefineDynamicModule(moduleName).DefineType(typeName, TypeAttributes.Public);
typeBuilder.DefineDefaultConstructor(MethodAttributes.Public);
return typeBuilder;
}
public static void CreateAutoImplementedProperty(TypeBuilder builder, string propertyName, Type propertyType)
{
const string PrivateFieldPrefix = "m_";
const string GetterPrefix = "get_";
const string SetterPrefix = "set_";
// Generate the field.
FieldBuilder fieldBuilder = builder.DefineField(string.Concat(PrivateFieldPrefix, propertyName), propertyType, FieldAttributes.Private);
// Generate the property
PropertyBuilder propertyBuilder = builder.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, null);
// Property getter and setter attributes.
MethodAttributes propertyMethodAttributes = MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig;
// Define the getter method.
MethodBuilder getterMethod = builder.DefineMethod(string.Concat(GetterPrefix, propertyName), propertyMethodAttributes, propertyType, Type.EmptyTypes);
// Emit the IL code.
// ldarg.0
// ldfld,_field
// ret
ILGenerator getterILCode = getterMethod.GetILGenerator();
getterILCode.Emit(OpCodes.Ldarg_0);
getterILCode.Emit(OpCodes.Ldfld, fieldBuilder);
getterILCode.Emit(OpCodes.Ret);
// Define the setter method.
MethodBuilder setterMethod = builder.DefineMethod(string.Concat(SetterPrefix, propertyName), propertyMethodAttributes, null, new Type[] { propertyType });
// Emit the IL code.
// ldarg.0
// ldarg.1
// stfld,_field
// ret
ILGenerator setterILCode = setterMethod.GetILGenerator();
setterILCode.Emit(OpCodes.Ldarg_0);
setterILCode.Emit(OpCodes.Ldarg_1);
setterILCode.Emit(OpCodes.Stfld, fieldBuilder);
setterILCode.Emit(OpCodes.Ret);
propertyBuilder.SetGetMethod(getterMethod);
propertyBuilder.SetSetMethod(setterMethod);
}
}
}
EF实体查询出的数据List<T>转DataTable出现【DataSet 不支持 System.Nullable<>】的问题
public static DataTable ToDataTable<T>(this IEnumerable<T> varlist, CreateRowDelegate<T> fn)
{
DataTable dtReturn = new DataTable();
// column names
PropertyInfo[] oProps = null;
// Could add a check to verify that there is an element 0
foreach (T rec in varlist)
{
// Use reflection to get property names, to create table, Only first time, others will follow
if (oProps == null)
{
oProps = ((Type)rec.GetType()).GetProperties();
foreach (PropertyInfo pi in oProps)
{
Type colType = pi.PropertyType; if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof(Nullable<>)))
{
colType = colType.GetGenericArguments()[0];
}
dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
}
}
DataRow dr = dtReturn.NewRow(); foreach (PropertyInfo pi in oProps)
{
dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue(rec, null);
}
dtReturn.Rows.Add(dr);
}
return (dtReturn);
}
public delegate object[] CreateRowDelegate<T>(T t);
List<T> list = DAL.ToList();
dataGridView1.DataSource = list.ToDataTable(a => new object[] { list });
以上代码可解决