Xamarin Master and MasterDetailPage InvalidOperationException

Question

I am not sure why I am getting this error I have read alot about this error and sounds like it is related to the title in the xaml file not being set. All my pages have the title set. The error is coming from the app.xaml.cs MainPage= new MainPage();

is there something else that can trigger this exeception?

System.InvalidOperationException: Master and Detail must be set before adding MasterDetailPage to a container

MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<MasterDetailPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:pages="clr-namespace:ReimbursementApp.Pages"
             x:Class="ReimbursementApp.Pages.MainPage"
             xmlns:telerikPrimitives="clr-namespace:Telerik.XamarinForms.Primitives;assembly=Telerik.XamarinForms.Primitives"
             Title="Main">

    <MasterDetailPage.Master>
        <pages:MenuPage />
    </MasterDetailPage.Master>

</MasterDetailPage>

MenuPage.xaml

<?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="ReimbursementApp.Pages.MenuPage"
             xmlns:telerikPrimitives="clr-namespace:Telerik.XamarinForms.Primitives;assembly=Telerik.XamarinForms.Primitives"
             xmlns:telerik="clr-namespace:Telerik.XamarinForms.DataControls;assembly=Telerik.XamarinForms.DataControls"
             Title="Menu">
    <!--<ContentPage.ToolbarItems>
        <ToolbarItem Activated="OnToolbarButtonClick" Order="Primary" Priority="0" Icon="hamburgerButtonIcon"/>
    </ContentPage.ToolbarItems>
    <Grid>
        <telerikPrimitives:RadSideDrawer x:Name="drawer" DrawerLength="250">
        </telerikPrimitives:RadSideDrawer>
    </Grid>-->

    <StackLayout VerticalOptions="FillAndExpand">
        <ListView x:Name="ListViewMenu"
                    HasUnevenRows="True">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Grid Padding="10">
                            <Label Text="{Binding Title}" FontSize="20"/>
                        </Grid>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage>

Gerald Versluis Gerald Versluis · Accepted Answer · 2019-02-27T14:51:27

The error message is literally saying what's wrong:

Master and Detail must be set before adding MasterDetailPage to a container

You already have set something in the Master property, like this:

<MasterDetailPage.Master> 
    <pages:MenuPage />
</MasterDetailPage.Master>

But you should also set the Detail property, something like this:

<MasterDetailPage.Detail> 
    <pages:MyMainPage />
</MasterDetailPage.Detail>

The MasterDetailPage is only a container and must have both a master (usually a menu) and a detail (something picked from the menu) to show something useful.

Xamarin Master and MasterDetailPage InvalidOperationException

2 Answers