如何从对象类型定义泛型类型？

Question

我有一个扩展方法:

public static List<object> ToModelViewObjectList<ModelViewType>(this IEnumerable<object> source)
{

    List<ModelViewType> destinationList = new List<ModelViewType>();

    PropertyInfo[] ModelViewProperties = typeof(ModelViewType).GetProperties();
    foreach (var sourceElement in source)
    {
        object destElement = Activator.CreateInstance<ModelViewType>();
        foreach (PropertyInfo sourceProperty in sourceElement.GetType().GetProperties())
        {

            if (ModelViewProperties.Select(m => m.Name).Contains(sourceProperty.Name))
            {
                destElement.GetType().GetProperty(sourceProperty.Name).SetValue(destElement, sourceProperty.GetValue(sourceElement));
            }
        }
        destinationList.Add((ModelViewType)destElement);
    }

    return destinationList.Cast<object>().ToList();
}

我有一个方法,其中包含一个对象列表,我希望在此方法中使用调用扩展方法:

public void GridModel(IEnumerable<object> GridDataSource)        
{ 
   List<object> list = GridDataSource.ToModelViewObjectList<GridDataSource[0].GetType()>();
}

我应该写什么而不是GridDataSource [0] .GetType()？

编辑:

我有一个带对象参数的方法.我想创建一个对象类型的通用列表.

public void CreateListByNonGenericType(object myObject)
{
    Type objType = myObject.GetType();

    var lst = System.Collections.Generic.List < objType.MakeGenericType() > ();
}

我应该写什么而不是objType.MakeGenericType()？

Answer 1

我应该写什么而不是GridDataSource[0].GetType()？

因为您在编译时不知道类型,所以必须在运行时执行所有操作.所以你需要从方法定义中创建一个泛型方法并调用它.如下:

GridModel(IEnumerable<object> GridDataSource)        
{ 
   Type dataSourceElementType = GridDataSource[0].GetType();

   //MyExtension is a type where ToModelViewObjectList defined
   MethodInfo methodDefinition = typeof(MyExtension).GetMethod("ToModelViewObjectList");

   //https://msdn.microsoft.com/en-us/library/system.reflection.methodinfo.makegenericmethod
   MethodInfo method = methodDefinition.MakeGenericMethod(dataSourceElementType)

   //https://msdn.microsoft.com/en-us/library/a89hcwhh
   List<object> list = (List<object>)method.Invoke(GridDataSource, null);
}

但是你真正想做的是接受ToModelViewObjectList的类型作为参数而不是泛型类型参数,如下所示,因为在返回对象列表时不要在函数外部使用ModelViewType.此外,它将使您的代码清晰.

public static List<object> ToModelViewObjectList(this IEnumerable<object> source, Type modelViewType)
{
    List<object> destinationList = new List<object>();

    PropertyInfo[] ModelViewProperties = modelViewType.GetProperties();
    foreach (var sourceElement in source)
    {
        object destElement = Activator.CreateInstance(modelViewType);
        foreach (PropertyInfo sourceProperty in sourceElement.GetType().GetProperties())
        {

            if (ModelViewProperties.Select(m => m.Name).Contains(sourceProperty.Name))
            {
                destElement.GetType().GetProperty(sourceProperty.Name).SetValue(destElement, sourceProperty.GetValue(sourceElement));
            }
        }
        destinationList.Add(destElement);
    }

    return destinationList;
}

所以你可以像你想的那样调用这个扩展方法:

List<object> list = GridDataSource.ToModelViewObjectList(GridDataSource[0].GetType());

此外,使用其他东西获取GridDataSource的元素类型比获取第一个元素的类型更好.

Answer 2

public void CreateListByNonGenericType(object myObject)
{
    Type objType = myObject.GetType();
    Type listType = typeof(List<>).MakeGenericType(objType);

    //We can not use here generic version of the interface, as we
    // do not know the type at compile time, so we use the non generic 
    // interface IList which will enable us to Add and Remove elements from
    // the collection
    IList lst = (IList)Activator.CreateInstance(listType);
}