C# 表达式目录树的应用详解

使用表达式目录树实现两个不同类型的属性赋值：

public class People
{
public int Age { get; set; }
public string Name { get; set; }
public int Id;
}
public class PeopleCopy
{
public int Age { get; set; }
public string Name { get; set; }
public int Id;
}
public class Class1
{
private static Dictionary<string, object> _Dic = new Dictionary<string, object>();
private static TOut TransExp<TIn, TOut>(TIn tIn) {
string key = $"funckey_{typeof(TIn).FullName}_{typeof(TOut).FullName}";
if (!_Dic.Keys.Contains(key)) {
ParameterExpression parameterExpression = Expression.Parameter(typeof(TIn), "p");
List<MemberBinding> memberBindingList = new List<MemberBinding>();
foreach (var item in typeof(TOut).GetProperties())
{
PropertyInfo propertyInfo = typeof(TIn).GetProperty(item.Name);
if (propertyInfo == null) { continue; }
MemberExpression property = Expression.Property(parameterExpression, propertyInfo);
memberBindingList.Add(Expression.Bind(item, property));
}
foreach (var item in typeof(TOut).GetFields())
{
FieldInfo fieldInfo = typeof(TIn).GetField(item.Name);
if (fieldInfo == null) { continue; }
MemberExpression property = Expression.Field(parameterExpression, fieldInfo);
memberBindingList.Add(Expression.Bind(item, property));
}
Expression<Func<TIn, TOut>> expression = Expression.Lambda<Func<TIn, TOut>>(Expression.MemberInit(Expression.New(typeof(TOut)), memberBindingList), new ParameterExpression[]
{
parameterExpression
});
Func<TIn, TOut> func = expression.Compile();
_Dic.Add(key,func);
}
return ((Func < TIn, TOut > )_Dic[key])(tIn);
}
}
static void Main(string[] args)
{
List<ClassLibrary1.PeopleCopy> PeoleCopyList = new List<ClassLibrary1.PeopleCopy>();
for (int i = 0; i < 5; i++)
{
ClassLibrary1.People people = new ClassLibrary1.People() { Id = 5+1, Age = 25, Name = "aaa"+i };
PeoleCopyList.Add(Class1.ToutGet<ClassLibrary1.People, ClassLibrary1.PeopleCopy>(people));
}
}

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