如何设置则selectedItem [英] How to set the selecteditem

问题描述

我想设置一个listpicker控件的值/ selectedItem设置 - 从Silverlight工具包为Windows Phone 7，当用户希望编辑XML条目（，它拉出来的数据的IO，并将其设置在文。盒/ listpickers）

我目前正在使用：

  ListPickerSub.SelectedItem =子; 
  

（子是一个字符串）

但它抛出一个System.InvalidOperationException

 附加信息：必须的SelectedItem始终被设置为一个有效的值。 
  

解决方案

的SelectedItem 期待一个ListPickerItem（这是在列表中的项目中的一个）。你传递给它一个字符串 - 因此误差

您可能会发现更容易将的SelectedIndex 。

这是很难给设置的SelectedItem不知道什么你填充与列表的一个例子。

编辑：结果
这里是你怎么可以绑定到字符串的例子。如果没有你实际上是绑定到的ItemSource一个可行的例子，这是最好的兴田我能做到的。 （只给该对象或部分代码的名称是远远不够的。）

假设：

 <控制：ListPicker X：NAME =ListPickerSub> 
<控制：ListPicker.ItemTemplate> 
<&DataTemplate的GT; 
< TextBlock的文本={结合}/> 
< / DataTemplate中> 
< /控制：ListPicker.ItemTemplate> 
<控制：ListPicker.FullModeItemTemplate> 
<&DataTemplate的GT; 
< TextBlock的文本={结合}/> 
< / DataTemplate中> 
< /控制：ListPicker.FullModeItemTemplate> 
< /控制：ListPicker> 
  

然后，我可以与内容绑定：

  ListPickerSub.ItemsSource =子项目（）; 
 
 
私人的IEnumerable<串GT;子项目（）
 {
收益率的回报星期一; 
收益率的回报星期二; 
收益率的回报周三 
收益率的回报星期四; 
收益率的回报星期五; 
收益率的回报星期六; 
收益率的回报星期日; 
} 
  

和设置的SelectedItem 与

  ListPickerSub.SelectedItem =星期天; 
  

I am trying to set the value/selecteditem of a listpicker control - from the silverlight toolkit for windows phone 7 (when the user wants to edit an entry in xml, it pulls the data out of IO and sets it in the text boxes/listpickers).

I am currently trying to use:

ListPickerSub.SelectedItem = sub;

(sub is a string)

But it is throwing a System.InvalidOperationException

Additional information: SelectedItem must always be set to a valid value.

解决方案

SelectedItem is expecting a ListPickerItem (which is one of the items in the list). You're passing it a string - hence the error.

You may find it easier to set the SelectedIndex.

It's hard to give a relevant example of setting the SelectedItem without knowing what you're populating the list with.

Edit:
Here's an example of how you could bind to strings. Without a workable example of what you are actually binding to the itemsource this is hte best I can do. (Just giving the name of the object or partial code isn't enough.)

Assuming:

<Controls:ListPicker x:Name="ListPickerSub">
    <Controls:ListPicker.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding}" />
        </DataTemplate>
    </Controls:ListPicker.ItemTemplate>
    <Controls:ListPicker.FullModeItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding}" />
        </DataTemplate>
    </Controls:ListPicker.FullModeItemTemplate>
</Controls:ListPicker>

Then I can bind the contents with:

ListPickerSub.ItemsSource = SubItems();


private IEnumerable<string> SubItems()
{
    yield return "monday";
    yield return "tuesday";
    yield return "wednesday";
    yield return "thursday";
    yield return "friday";
    yield return "saturday";
    yield return "sunday";
}

and set the SelectedItem with:

ListPickerSub.SelectedItem = "sunday";

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