"Sequence contains elements“错误

Question

在一个简单的xaml表单中，我得到了错误"Sequence contains no elements“。我对Xamarin表单相当陌生，所以请容忍我。

有什么想法吗？

<?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="CRM.Views.CustomerItem" Title="Customer Info">

<ContentPage.Content>

    <StackLayout Padding="10" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">

        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>
            <Label Text="Name" Grid.Row="0" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
            <Entry Text="{Binding CustName}" Grid.Row="0" Grid.Column="1"/>
            <Label Text="Surname" Grid.Row="1" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
            <Entry Text="{Binding CustSurname}" Grid.Row="1" Grid.Column="1"/>
            <Label Text="Address" Grid.Row="2" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
            <Entry Text="{Binding Address}" Grid.Row="2" Grid.Column="1"/>
            <Label Text="PhoneNumber" Grid.Row="3" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
            <Entry Text="{Binding PhoneNumber}" Grid.Row="3" Grid.Column="1"/>
        </Grid>
    </StackLayout>

    <Button Text="Save" HorizontalOptions="FillAndExpand" BackgroundColor="Blue" TextColor="White" Clicked="Save_Clicked"></Button>
    <Button Text="Cancel" HorizontalOptions="FillAndExpand" BackgroundColor="Red" TextColor="White" Clicked="Cancel_Clicked"></Button>

</ContentPage.Content>

​

Answer 1

始终确保ContentPage.Content只有一个布局控件，如StackLayout或Grid等，以及它们内部的所有其他控件。

<ContentPage.Content>
   <StackLayout>
       <!-- all controls go here -->
   </StackLayout>
</ContentPage.Content>

这将会解决这个问题

Answer 2

按钮很好，但是网格没有定义行，但是您使用的是Grid.Row="0“。由于序列中没有行，因此它会显示"Sequence contains no elements“。

尝试添加行定义

​

<StackLayout Padding="10" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">

    <Grid>
        <Grid.RowDefinitions>
             <RowDefinition Height="100" />
             <RowDefinition Height="100" />
             <RowDefinition Height="100" />
             <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Label Text="Name" Grid.Row="0" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
        <Entry Text="{Binding CustName}" Grid.Row="0" Grid.Column="1"/>
        <Label Text="Surname" Grid.Row="1" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
        <Entry Text="{Binding CustSurname}" Grid.Row="1" Grid.Column="1"/>
        <Label Text="Address" Grid.Row="2" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
        <Entry Text="{Binding Address}" Grid.Row="2" Grid.Column="1"/>
        <Label Text="PhoneNumber" Grid.Row="3" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
        <Entry Text="{Binding PhoneNumber}" Grid.Row="3" Grid.Column="1"/>
    </Grid>
</StackLayout>

<Button Text="Save" HorizontalOptions="FillAndExpand" BackgroundColor="Blue" TextColor="White" Clicked="Save_Clicked"></Button>
<Button Text="Cancel" HorizontalOptions="FillAndExpand" BackgroundColor="Red" TextColor="White" Clicked="Cancel_Clicked"></Button>

​

Answer 3

You Must be Create Rows and Columns Both...

<Grid>
      <Grid.RowDefinitions>
        <RowDefinition Height="2*" />
        <RowDefinition Height="*" />
        <RowDefinition Height="200" />
      </Grid.RowDefinitions>
      <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="*" />
      </Grid.ColumnDefinitions>
    </Grid>