当绑定到POCO的列表时，指定的演员表无效 [英] Specified cast is not valid when binding to list of POCO's

问题描述

好，所以我有以下观点:

Ok so I have the following view:

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="BoomSauce.MainPage">
  <ListView ItemsSource="{Binding Model.MyPocos}">
    <ListView.ItemTemplate>
      <DataTemplate>
        <Label Text="{Binding MyString}"></Label>
      </DataTemplate>
    </ListView.ItemTemplate>
  </ListView>
</ContentPage>

此视图的BindingContext是以下ViewModel:

The BindingContext of this view is the following ViewModel:

public class MainViewModel
{
    public MainModel Model { get; set; }
}

这是MainModel:

Here is MainModel:

public class MainModel
{
    public List<MyPoco> MyPocos { get; set; }
}

这是MyPoco:

public class MyPoco
{
    public string MyString { get; set; }
    public int MyInt { get; set; }
}

这是App()中发生的事情

Here's what's going on in App()

MainPage = new MainPage();

var viewModel = new MainViewModel
{
    Model = new MainModel
    {
        MyPocos = new List<MyPoco>()
        {
            new MyPoco() { MyInt = 1, MyString = "a" }, 
            new MyPoco() { MyInt = 2, MyString = "b" }, 
            new MyPoco() { MyInt = 3, MyString = "c" }, 
            new MyPoco() { MyInt = 4, MyString = "d" }, 
            new MyPoco() { MyInt = 5, MyString = "e" }
        }
    }
};

MainPage.BindingContext = viewModel;

真的没有别的了，我得到了以下异常:

Really nothing else to it, I am getting the following exception:

指定的演员表无效.

Specified cast is not valid.

但据我所知我做的一切正确，但没有内部异常，也没有更多的上下文.

But no inner exception and no more context, as far as I can tell I'm doing everything correctly.

绑定到字符串列表可以很好地工作，这是在我将其替换为任何其他对象时出现问题的原因.

Binding to a list of strings works fine, it's when I replace that with any other object that things go wrong.

关于我要去哪里的任何想法吗?

Any ideas on where I'm going wrong?

谢谢

推荐答案

原来，您不能将Label直接放在DataTemplate内，而必须将其嵌套在ViewCell中，就像这样:

It turns you can't put a Label directly inside a DataTemplate, you instead have to nest this in a ViewCell, like so:

<ViewCell>
    <ViewCell.View>
        <Label Text="{Binding MyString}" />
    </ViewCell.View>
</ViewCell>

神秘感解决了.

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