我有那个lambda:
var Ids = profileExample.CostCenters
.Where(CostCentre => CostCentre != null)
.Select(CostCentre => CostCentre.Id);
然后转换为表达式树
static IEnumerable<Int64> AboveLambdaConvertedToExpressionTree(Profile profileExample)
{
//Begin var Ids = profileExample.CostCenters.Where(CostCentre => CostCentre != null).Select(CostCentre => CostCentre.Id);
var property = profileExample.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance).Where(x => x.Name != "Id").First();
var collection = ((IEnumerable)property.GetValue(profileExample, null)).AsQueryable();
var collectionType = property.PropertyType.GetGenericArguments()[0];
var collectionTypeName = collectionType.Name;
var keyType = typeof(Int64);
var keyName = "Id";
//BeginWhere
var parameter = Expression.Parameter(collectionType, collectionTypeName);
var profileExampleWhere = Expression.Lambda(
Expression.NotEqual(parameter, Expression.Constant(null)),
parameter);
var profileExampleWhereCall = Expression.Call(typeof(Enumerable),
"Where",
new Type[] { collectionType },
collection.Expression,
profileExampleWhere);
//EndWhere
//BeginSelect
var profileExampleSelect = Expression.Lambda(Expression.PropertyOrField(parameter, keyName),
parameter);
var profileExampleSelectCall = Expression.Call(typeof(Enumerable),
"Select",
new Type[] { collectionType, keyType },
profileExampleWhereCall,
profileExampleSelect);
var Ids = Expression.Lambda(profileExampleSelectCall).Compile().DynamicInvoke();
//EndSelect
//End var Ids = profileExample.CostCenters.Where(CostCentre => CostCentre != null).Select(CostCentre => CostCentre.Id);
return ((IEnumerable)Ids).Cast<Int64>();
}
现在我想对bellow lambda
做同样的事情var result = Set.AsQueryable()
.Where(Profile => Profile.CostCenters.Select(CostCentre => CostCentre.Id)
.Any(Id => Ids.Contains(Id))).ToList();
但是我卡在.Any(Id => Ids.Contains(Id))....
var id = Expression.Parameter(typeof(long), "Id");
var costCentre = Expression.Parameter(typeof(CostCentre), "CostCentre");
var profile = Expression.Parameter(typeof(Profile), "Profile");
var selectLambda = Expression.Lambda(Expression.PropertyOrField(costCentre, "Id"), costCentre);
var selectCall = Expression.Call(typeof(Enumerable),
"Select",
new Type[] { typeof(CostCentre), typeof(long) },
Expression.PropertyOrField(profile, "CostCenters"),
selectLambda);
如何从selectCall和call id . contains…
作为控制台应用程序运行的完整代码如下:
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
namespace ExpressionTrees
{
class Program
{
static void Main(string[] args)
{
var Ids = profileExample.CostCenters.Where(CostCentre => CostCentre != null).Select(CostCentre => CostCentre.Id);
Ids = AboveLambdaConvertedToExpressionTree(profileExample);
var result = Set.AsQueryable().Where(Profile => Profile.CostCenters.Select(CostCentre => CostCentre.Id).Any(Id => Ids.Contains(Id))).ToList();
//Expression<Func<Profile, bool>> lambda = (Profile) => Profile.CostCenters.Select(CostCentre => CostCentre.Id).Any(Id => Ids.Contains(Id));
var id = Expression.Parameter(typeof(long), "Id");
var costCentre = Expression.Parameter(typeof(CostCentre), "CostCentre");
var profile = Expression.Parameter(typeof(Profile), "Profile");
var selectLambda = Expression.Lambda(Expression.PropertyOrField(costCentre, "Id"), costCentre);
var selectCall = Expression.Call(typeof(Enumerable),
"Select",
new Type[] { typeof(CostCentre), typeof(long) },
Expression.PropertyOrField(profile, "CostCenters"),
selectLambda);
}
static IEnumerable<Int64> AboveLambdaConvertedToExpressionTree(Profile profileExample)
{
// I show that as example of what i need to do
var keyType = typeof(Int64);
var keyName = "Id";
//Begin var Ids = profileExample.CostCenters.Where(CostCentre => CostCentre != null).Select(CostCentre => CostCentre.Id);
var property = profileExample.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance).Where(x => x.Name != keyName).First();
var collection = ((IEnumerable)property.GetValue(profileExample, null)).AsQueryable();
var collectionType = property.PropertyType.GetGenericArguments()[0];
var collectionTypeName = collectionType.Name;
//BeginWhere
var parameter = Expression.Parameter(collectionType, collectionTypeName);
var profileExampleWhere = Expression.Lambda(
Expression.NotEqual(parameter, Expression.Constant(null)),
parameter);
var profileExampleWhereCall = Expression.Call(typeof(Enumerable),
"Where",
new Type[] { collectionType },
collection.Expression,
profileExampleWhere);
//EndWhere
//BeginSelect
var profileExampleSelect = Expression.Lambda(Expression.PropertyOrField(parameter, keyName),
parameter);
var profileExampleSelectCall = Expression.Call(typeof(Enumerable),
"Select",
new Type[] { collectionType, keyType },
profileExampleWhereCall,
profileExampleSelect);
var Ids = Expression.Lambda(profileExampleSelectCall).Compile().DynamicInvoke();
//EndSelect
//End var Ids = profileExample.CostCenters.Where(CostCentre => CostCentre != null).Select(CostCentre => CostCentre.Id);
return ((IEnumerable)Ids).Cast<Int64>();
}
public partial class Profile
{
public virtual Int64 Id { get; set; }
public virtual ICollection<CostCentre> CostCenters { get; set; }
}
public partial class CostCentre
{
public virtual Int64 Id { get; set; }
}
public static Profile profileExample
{
get
{
return new Profile()
{
Id = 1,
CostCenters = new List<CostCentre>() { new CostCentre() { Id = 2 } }
};
}
}
public static IList<Profile> Set
{
get
{
return new List<Profile>() { new Profile() { Id = 1,
CostCenters = new List<CostCentre>() { new CostCentre() { Id = 1 },
new CostCentre() { Id = 2 } }
},
new Profile() { Id = 2,
CostCenters = new List<CostCentre>() { new CostCentre() { Id = 2 },
new CostCentre() { Id = 3 } }
},
new Profile() { Id = 3,
CostCenters = new List<CostCentre>() { new CostCentre() { Id = 3 } }
} };
}
}
}
}
由于Any是Generic Method，您需要为特定类型创建它。下面的方法从Enumerable类型得到Any<T>方法。
public static MethodInfo GetAnyExtensionMethod(Type forType)
{
MethodInfo method =
typeof(Enumerable).GetMethods()
.First(m => m.Name.Equals("Any") &&
m.GetParameters().Count() == 2);
return method.MakeGenericMethod(new[] { forType });
}
在MS的帮助下解决了这个问题
class Program
{
static void Main(string[] args)
{
//var Ids = profileExample.CostCenters.Where(CostCentre => CostCentre != null).Select(CostCentre => CostCentre.Id);
var Ids = AboveLambdaConvertedToExpressionTree(profileExample);
//var result = Set.AsQueryable().Where(Profile => Profile.CostCenters.Select(CostCentre => CostCentre.Id).Any(Id => Ids.Contains(Id))).ToList();
var id = Expression.Parameter(typeof(long), "Id");
var costCentre = Expression.Parameter(typeof(CostCentre), "CostCentre");
var profile = Expression.Parameter(typeof(Profile), "Profile");
var selectLambda = Expression.Lambda(Expression.PropertyOrField(costCentre, "Id"), costCentre);
var selectCall = Expression.Call(typeof(Enumerable),
"Select",
new Type[] { typeof(CostCentre), typeof(long) },
Expression.PropertyOrField(profile, "CostCenters"),
selectLambda);
//var id2 = Expression.Parameter(typeof(long), "Id");
var containsCall = Expression.Call(typeof(Enumerable),
"Contains",
new Type[] { typeof(long) },
Expression.Constant(Ids),
id);
var anyLambda = Expression.Lambda(containsCall, id);
var anyCall = Expression.Call(typeof(Enumerable),
"Any",
new Type[] { typeof(long) },
selectCall,
anyLambda);
var whereLambda = Expression.Lambda(anyCall, profile);
var callExpression = Expression.Call(typeof(Queryable),
"Where",
new Type[] { typeof(Profile) },
Set.AsQueryable().Expression,
whereLambda);
var result = Expression.Lambda(callExpression).Compile().DynamicInvoke();
}