创建动态函数< T，TResult>。来自对象 [英] Create Dynamic Func<T, TResult> from Object
问题描述
我有一个criteria对象，如果该属性的值不为null，我将其中的每个属性都转换为一个func。 c>公共类TestClassCriteria
{
公共布尔？ ColumnA {get;组; }
公共布尔？ ColumnB {get;组; }
}
这是我到目前为止的内容，但是我很确定自己是没有正确定义lambda。这就是我想要实现的目标。 funcs.Add（x => x.ColumnA ==条件.ColumnA）。
var属性=条件.GetType（）。GetProperties（）;
var funcs = new List< Func< dynamic，bool>>（）;
foreach（属性中的var属性）
{
var propertyName = property.Name;
funcs.Add（x => x.GetType（）。GetProperty（propertyName）.Name ==条件.GetType（）。GetProperty（propertyName）.Name）;
}
它没有崩溃或引起任何错误，它只是无法正常工作。 / p>
您能提供的任何帮助将不胜感激。
您想要这样的东西吗？ GetCriteriaFunctions< TEntity，TCriteria>（）
{
varcriteriasFunctions = new List< Func< TEntity，TCriteria，bool>（）;
//搜索条件
的可空属性varcriteriaProperties = typeof（TCriteria）
.GetProperties（）
。where（p => p.PropertyType。 IsGenericType& p.PropertyType.GetGenericTypeDefinition（）== typeof（Nullable<>））;
foreach（criteriaProperties中的var属性）
{
//这是实体参数
var entityParameterExpression = Expression.Parameter（typeof（TEntity））;
//这是标准参数
var条件ParameterExpression = Expression.Parameter（typeof（TCriteria））;
//这是标准属性访问： criteria.SomeProperty
varcriteriaPropertyExpression = Expression.Property（criteriaParameterExpression，property）;
//测试标准属性和实体属性之间是否相等；
//注意，criteria属性应首先转换；
// //此代码也假定实体和条件属性具有相同的名称
var testingForEqualityExpression = Expression.Equal（
Expression.Convert（criteriaPropertyExpression，property.PropertyType.GetGenericArguments（） [0]），
Expression.Property（entityParameterExpression，property.Name））;
//条件。SomeProperty== null？ true：（（（EntityPropertyType）criteria.SomeProperty == entity.SomeProperty）
var体= Expression.Condition（
Expression.Equal（criteriaPropertyExpression，Expression.Constant（null）），
Expression。常量（true），
testingForEqualityExpression）;
//让我们将lambda编译为方法
var条件函数= Expression.Lambda< Func< TEntity，TCriteria，bool>（body，EntityParameterParameterion，criteriaParameterParameterExpression）.Compile（）;
criteriaFunctions.Add（criteriaFunction）;
}
返回条件函数；
}
样本实体和样本标准：
类CustomerCriteria
{
public int？年龄{get;组; }
公共布尔？ IsNew {得到;组; }
}
类客户
{
公共字符串名称{get;组; }
public int年龄{get;组; }
public bool IsNew {get;组; }
}
用法：
var条件函数= GetCriteriaFunctions< Customer，CustomerCriteria>（）;
var customer1 =新客户{名称= John，年龄= 35，IsNew = false};
var customer2 =新客户{名称= Mary，年龄= 27，IsNew = true};
var条件1 =新的CustomerCriteria {年龄= 35}；
var条件2 =新的CustomerCriteria {IsNew = true};
Console.WriteLine（ Is match：{0}，criteriaFunctions.All（f => f（customer1，criteria1）））;
Console.WriteLine（ Is match：{0}，criteriaFunctions.All（f => f（customer2，criteria1）））;
Console.WriteLine（ Is match：{0}，criteriaFunctions.All（f => f（customer1，criteria2）））;
Console.WriteLine（ Is match：{0}，criteriaFunctions.All（f => f（customer2，criteria2）））;
此代码不是使用动态代码，而是使用强类型成员访问，因此，您可以缓存列表每对实体-条件和测试实例的条件匹配速度更快。
I have a criteria object in which I was to turn each property into a func, if it's value isn't null.
public class TestClassCriteria
{
public bool? ColumnA { get; set; }
public bool? ColumnB { get; set; }
}
This is what I have thus far, but I am pretty sure I am not defining the lambda correct. This is what I trying to achieve. funcs.Add(x => x.ColumnA == criteria.ColumnA).
var properties = criteria.GetType().GetProperties();
var funcs = new List<Func<dynamic, bool>>();
foreach (var property in properties)
{
var propertyName = property.Name;
funcs.Add(x => x.GetType().GetProperty(propertyName).Name == criteria.GetType().GetProperty(propertyName).Name);
}
It's not crashing or causing any error, it just isn't working.
Any help you can provide would be greatly appreciated.
Do you want something like this?
static List<Func<TEntity, TCriteria, bool>> GetCriteriaFunctions<TEntity, TCriteria>()
{
var criteriaFunctions = new List<Func<TEntity, TCriteria, bool>>();
// searching for nullable properties of criteria
var criteriaProperties = typeof(TCriteria)
.GetProperties()
.Where(p => p.PropertyType.IsGenericType && p.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>));
foreach (var property in criteriaProperties)
{
// this is entity parameter
var entityParameterExpression = Expression.Parameter(typeof(TEntity));
// this is criteria parameter
var criteriaParameterExpression = Expression.Parameter(typeof(TCriteria));
// this is criteria property access: "criteria.SomeProperty"
var criteriaPropertyExpression = Expression.Property(criteriaParameterExpression, property);
// this is testing for equality between criteria property and entity property;
// note, that criteria property should be converted first;
// also, this code makes assumption, that entity and criteria properties have the same names
var testingForEqualityExpression = Expression.Equal(
Expression.Convert(criteriaPropertyExpression, property.PropertyType.GetGenericArguments()[0]),
Expression.Property(entityParameterExpression, property.Name));
// criteria.SomeProperty == null ? true : ((EntityPropertyType)criteria.SomeProperty == entity.SomeProperty)
var body = Expression.Condition(
Expression.Equal(criteriaPropertyExpression, Expression.Constant(null)),
Expression.Constant(true),
testingForEqualityExpression);
// let's compile lambda to method
var criteriaFunction = Expression.Lambda<Func<TEntity, TCriteria, bool>>(body, entityParameterExpression, criteriaParameterExpression).Compile();
criteriaFunctions.Add(criteriaFunction);
}
return criteriaFunctions;
}
Sample entity and sample criteria:
class CustomerCriteria
{
public int? Age { get; set; }
public bool? IsNew { get; set; }
}
class Customer
{
public string Name { get; set; }
public int Age { get; set; }
public bool IsNew { get; set; }
}
Usage:
var criteriaFunctions = GetCriteriaFunctions<Customer, CustomerCriteria>();
var customer1 = new Customer { Name = "John", Age = 35, IsNew = false };
var customer2 = new Customer { Name = "Mary", Age = 27, IsNew = true };
var criteria1 = new CustomerCriteria { Age = 35 };
var criteria2 = new CustomerCriteria { IsNew = true };
Console.WriteLine("Is match: {0}", criteriaFunctions.All(f => f(customer1, criteria1)));
Console.WriteLine("Is match: {0}", criteriaFunctions.All(f => f(customer2, criteria1)));
Console.WriteLine("Is match: {0}", criteriaFunctions.All(f => f(customer1, criteria2)));
Console.WriteLine("Is match: {0}", criteriaFunctions.All(f => f(customer2, criteria2)));
Instead of your code with dynamics, this code uses strongly typed member access, so, you could cache list of criteria for each pair "Entity - Criteria" and test instances form matching faster.
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