//private static string GetConvertName(Type type)
//{
// return ConvertMethodNames[type];
//}
/// <summary>将字典类型转换成对象的委托
/// </summary>
public static Func <Dictionary <string, object>, T> GetObjectFunc <T>() where T : class, new()
{
var sourceType = typeof(Dictionary <string, object>);
var targetType = typeof(T);
// define the parameter
var parameterExpr = Expression.Parameter(sourceType, "x");
//collect the body
var bodyExprs = new List <Expression>();
// 初始化对象
var objectExpr = Expression.Variable(targetType, "obj");
var newObjectExpr = Expression.New(targetType);
var assignObjectExpr = Expression.Assign(objectExpr, newObjectExpr);
bodyExprs.Add(assignObjectExpr);
//获取T的全部公有属性
var properties = PropertyInfoUtil.GetProperties(targetType);
foreach (var property in properties)
{
var nameExpr = Expression.Constant(property.Name);
var fieldExpr = Expression.PropertyOrField(objectExpr, property.Name);
//将object转换为对应的属性类型,int,double...
// 要调用索引必须先获取PropertyType类型
PropertyInfo indexer =
(from p in parameterExpr.Type.GetTypeInfo().GetDefaultMembers().OfType <PropertyInfo>()
// This check is probably useless. You can't overload on return value in C#.
where p.PropertyType == typeof(object)
let q = p.GetIndexParameters()
// Here we can search for the exact overload. Length is the number of "parameters" of the indexer, and then we can check for their type.
where q.Length == 1 && q[0].ParameterType == typeof(string)
select p).Single();
var indexValueExpr = Expression.Property(parameterExpr, indexer, nameExpr);
//属性值
var castIndexValueExpr = Expression.Convert(indexValueExpr, property.PropertyType);
//调用 Convert.ChangeType(object,xxx)
//var convertMethodExpr = Expression.Call(null,
/* 另外的代码, typeof(Convert).GetTypeInfo().GetMethod(GetConvertName(property.PropertyType), new Type[] { typeof(object) }), indexValueExpr);*/
var assignFieldExpr = Expression.Assign(fieldExpr, castIndexValueExpr);
var notNullExpr = Expression.IfThen(Expression.NotEqual(indexValueExpr, Expression.Constant(null)),
assignFieldExpr);
//contains方法
var containMethodExpr = Expression.Call(parameterExpr,
sourceType.GetTypeInfo().GetMethod("ContainsKey", new[] { typeof(string) }), nameExpr);
var ifContainExpr = Expression.IfThen(containMethodExpr, notNullExpr);
bodyExprs.Add(ifContainExpr);
}
//返回
bodyExprs.Add(objectExpr);
var methodBodyExpr = Expression.Block(targetType, new[] { objectExpr }, bodyExprs);
var lambdaExpr = Expression.Lambda <Func <Dictionary <string, object>, T> >(methodBodyExpr, parameterExpr);
var func = lambdaExpr.Compile();
return(func);
}
