如何设置属性选择器的值 Expression<Func<T,TResult>> [英] How set value a property selector Expression<Func<T,TResult>>
问题描述
我需要使用模式工厂的想法将我的 Person 类实体中的实体属性 Address 与我的 FactoryEntities 类中的表达式 linq 相关联,看看这就是我所拥有的,我想要做的:
i need associate a entity property Address in my Person class entity with expressions linq in my FactoryEntities class using pattern factory idea, look this is what I have and I want to do:
Address address = new Address();
address.Country = "Chile";
address.City = "Santiago";
address.ZipCode = "43532";
//Factory instance creation object
//This is idea
Person person = new FactoryEntity<Person>().AssociateWithEntity(p=>p.Address, address);
public class Person: Entity
{
public string Name{ get; set; }
public string LastName{ get; set; }
public Address Address{ get; set; }
}
public class Address: Entity
{
public string Country{ get; set; }
public string City{ get; set; }
public string ZipCode{ get; set; }
}
public class FactoryEntity<TEntity> where TEntity : Entity
{
public void AssociateWithEntity<TProperty>(Expression<Func<TEntity, TProperty>> entityExpression, TProperty newValueEntity) where TProperty : Entity
{
if (instanceEntity == null || instanceEntity.IsTransient())
throw new ArgumentNullException();
/*TODO: Logic the association and validation
How set the newValueEntity into the property of entityExpression (x=>x.Direccion = direccion*/
}
}
推荐答案
这是有效的:
以下辅助方法将 getter 表达式转换为 setter 委托.如果你想返回一个 Expression
而不是 Action
,只要不要调用 Compile()
方法末尾.
This works:
The following helper method converts a getter expression into a setter delegate. If you want to return an Expression<Action<T,TProperty>>
instead of an Action<T,TProperty>
, just don't call the Compile()
method at the end.
注意:代码来自 Ian Mercer 的博客:http://blog.abodit.com/2011/09/convert-a-property-getter-to-a-setter/
Note: The code is from Ian Mercer's blog: http://blog.abodit.com/2011/09/convert-a-property-getter-to-a-setter/
/// <summary>
/// Convert a lambda expression for a getter into a setter
/// </summary>
public static Action<T, TProperty> GetSetter<T, TProperty>(Expression<Func<T, TProperty>> expression)
{
var memberExpression = (MemberExpression)expression.Body;
var property = (PropertyInfo)memberExpression.Member;
var setMethod = property.GetSetMethod();
var parameterT = Expression.Parameter(typeof(T), "x");
var parameterTProperty = Expression.Parameter(typeof(TProperty), "y");
var newExpression =
Expression.Lambda<Action<T, TProperty>>(
Expression.Call(parameterT, setMethod, parameterTProperty),
parameterT,
parameterTProperty
);
return newExpression.Compile();
}
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