为什么我不能遍历匿名类型

Question

ControllerAction:

{

    AddLeadSourcesModel model = new AddLeadSourcesModel();
    List<LeadSourceModel> models = LeadSourceModel.Get()
                                                  .Where(c => c.Active == true)
                                                  .ToList();
    var A = LeadSourceModel.GetSubLeadSources(leadSourceID);
    model.LeadSources = new SelectList(
        LeadSourceModel.Get().Where(c => c.Active == true), 
        "LeadSourceID", 
        "Name", 
        models.Where(c => c.LeadSourceID == leadSourceID).FirstOrDefault().LeadSourceID
    );

    model.SubLeadSources = new SelectList(A, "LeadSourceID", "Name");

    var flattenedData = model.SubLeadSources.SelectMany(subLead => model.LeadSources, (n, a) => new { n,a });

    return PartialView("_AddLeadSources", flattenedData.ToList());

}

View:

<table>
    <tr>
        <td>Lead Source</td>
        <td>Sub Lead Source</td>
        <td>Action</td>
    </tr>
    @foreach(var item in Model)
    {
    <tr>
        <td>@item.a</td>
        <td>@item.n</td>
        <td><a href="#">Remove</a></td>
    </tr>
    }
</table>

My problem is when I get to the partial it says it expects a different type but I've not told it a type. And I technically don't know the type coz it's annoymous

How do I get this to work?

Answer 1

Somewhere you've defined class PartialView with a constructor that takes two parameters.

Alas you forgot to give us the signature of this constructor, but I think that the first one is a string, the second one is list / sequence / collection of some defined type. I expect something like:

class PartialView
{
     public PartialView(string txt, List<MyType> items) {...}
}

If you want to use this constructor you'll have to provide a List<MyType> . To do this, use Select before you create FlattenedData:

List<MyType> flattenedData = model.SubLeadSources
    .SelectMany(subLead => model.LeadSources, (n, a) => new { n,a })
    .Select(item => new MyType()
    {
        // fill the MyType properties, something like:
        N= item.n
        A = item.a,
    };

Now you can use the constructor.

PartialView partialView = new PartialView("_AddLeadSources", flattenedData);

Extension Function

If you'll convert quite often some anonymous type to a sequence of MyType and a PartialView, consider creating an extension function that will take as input a sequence of any (anonymous) type, a string, and two lambda expressions that will tell you which values of the anonymous types are the A and N.

See extension methods demystified

We already know that MyType has properties like A and an N, where you'd like to put your anonymous a and n in. Let's assume they have non-generic type Atype and Ntype, for instance int, or DateTime, or MyElaborateClass, like this:

class MyType
{
     public Atype A {get; set;}
     public Btype B {get; set;}
}

Extension class for PartialView:

static class PartialViewExtension
{
    // Creates one PartialView object from a sequence of MyType objects and a text
    public static PartialView ToPartialView(this IEnumerable<MyType> source, string text)
    {
         return  new PartialView(text, source.ToList());
    }

    // uses the source + predicates to create a sequence of MyType objects
    public static IEnumerable<MyType> ToMyType<TSource>(this IEnumerable<TSource> source,
        Func<TSource, Atype> aSelector,
        Func<TSource, Ntype> nSelector)
    {
         return source.Select(sourceItem => new MyType()
         {
              A = aSelector(sourceItem),
              B = bSelector(sourceItem),
         });
    }
}

Usage would be like:

var flattenedData = model.SubLeadSources
    .SelectMany(subLead => model.LeadSources, (n, a) => new { n,a });

PartialView partialView = flattenedData
      .ToMyType(flattenedInput => flattenedInput.n,
                flattendInput => flattenedInput.a)
      .ToPartialView("_AddLeadSources");

Now that we are already creating extension functions, lets combine these two into one, that will call the other two:

public static PartialView ToPartialView<TSource>(this IEnumerable<TSource> source,
    string text,
    Func<TSource, Atype> aSelector,
    Func<TSource, Ntype> nSelector)
{
    return source.ToMyType(aSelector, bSelector).ToPartialView(text);
}

Usage:

var flattenedData = model.SubLeadSources
    .SelectMany(subLead => model.LeadSources, (n, a) => new { n,a });

PartialView = flattenedData.ToPartialView("_AddLeadSources",
    flattenedInput => flattenedInput.a,
    flattenedInput => flattenedInput.n);