How to set a top margin only in XAML?

Question

I can set margins individually in code but how do I do it in XAML, e.g. how do I do this:

PSEUDO-CODE:

<StackPanel Margin.Top="{Binding TopMargin}">

Ramburt

Answer 1

The key is to realize that setting it in code like this:

sp2.Margin = new System.Windows.Thickness{ Left = 5 };

is equivalent to:

sp2.Margin = new System.Windows.Thickness{ Left = 5, Top = 0, Right = 0, Bottom = 0 };

You can't set just a single value in a Thickness instance through either code or XAML. If you don't set some of the values, they will be implicitly zero. Therefore, you can just do this to convert the accepted code sample in your other question to a XAML equivalent:

<StackPanel Margin="{Binding TopMargin, Converter={StaticResource MyConverter}}"/>

where MyConverter just returns a Thickness that sets only the Top and leaves all other values as zero.

Of course, you could write your own control that does expose these individual values as dependency properties to make your code a little cleaner:

<CustomBorder TopMargin="{Binding TopMargin}">
</CustomBorder>

A better option than a custom control would be to write an attached property and change the Thickness using the code above in the dependency property setter. The below code would be usable across ALL controls which have a Margin.

public static readonly DependencyProperty TopMarginProperty =
    DependencyProperty.RegisterAttached("TopMargin", typeof(int), typeof(FrameworkElement),
                                        new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.AffectsRender));
public static void SetTopMargin(FrameworkElement element, int value)
{
    // set top margin in element.Margin
}
public static int GetTopMargin(FrameworkElement element)
{
    // get top margin from element.Margin
}

If you couple this with a Behavior, you can get notification changes on the TopMargin property.

Fluorite

Simple, effective and I'm not sure why people try and complicate this. One line is far better than the 20 or so that some people think it takes. I appreciate this answer. – Concoff

You can set it like this var margin = sp2.Margin; margin.Left = 5; sp2.Margin = margin; This will leave the other values intact. – Studnia

@bugged87: the OP wanted to do it in XAML. – Fluorite

@KentBoogaart I know what the question asked for, but my comment was referring to your answer. You stated: "You can't set just a single value in a Thickness instance through either code or XAML". However, you can do it in code in the manner I suggested. – Studnia

@bugged87: You're still setting all values - you're just seeding them from what was already there. My point therefore stands. Had you not seeded your Thickness instance from the existing one, everything bar the Left would be 0. ie. there is no concept of an "unset" Top, Bottom, Left, or Right here because it's a value type. They're set either by your code or implicitly to 0. To also quote myself, the sentence directly after the one you quoted: "If you don't set some of the values, they will be implicitly zero." – Fluorite

@KentBoogaart I understand you're point now. But the fact that I was originally mislead is actually MY point. For example, my suggestion which involves "seeding" the other values from the current margin could be wrapped in a SetMarginLeft(int value) method whose implementation is completely hidden from the end user. In this sense, then, it is "possible" to set only a specific Thickness value. For many end users, perception is reality. – Studnia

A solution for this can be <StackPanel Margin="0,10,0,0" /> with no binding required ... – Herbart

Answer 2

Isn't this what you're looking for?

<StackPanel Margin="0,10,0,0" />

The first value is Left margin, then Top, then Right, and last but not least Bottom.

I'm not sure if you want to bind it to something, but if not, that'll work.

Beitch

No. This overwrites Left/Right/Bottom with "0". OP wanted to leave the existing margin (which likely comes from a style binding) and set only one side. As would I, but it appears that you can't without quite a bit of effort. – Boxcar

Answer 3

This belongs to the WPF/XAML commandments:

1. I am WPF/XAML, thy UI framework, and you will use me when coding apps for Windows - eventually.
2. Thou shalt have no other technologies - I will not be cross-platform but I'll try to with Silverlight UWP, because Hololens is going to be huge some day. _{"Xamarin.Forms"? Never heard of it!}
3. Thou shalt inevitably take the name of the Lord in vain, repeatedly, when using WPF/XAML.
4. Remember the sabbath day: every 7 days... or hours or minutes of coding I will make you take a break to go to StackOverflow and 2000things.
5. Honor thy father and mother: Windows Forms.
6. Should thou shalt adopt MVVM, thou shalt also implement INPC and INCC, but rejoice! Thou hast a choice: you can use it or you can use it with anger.
7. Thou shalt not commit adultery interop with other apps and frameworks.
8. Thou shalt not covet thy neighbour's UI framework.
9. Thou shalt not be able to set a position of an element dynamically using binding of an either attached property or margin without writing few lines of code-behind.
10. Thou shalt never have a simple bool Visibility property in XAML. I am WPF/XAML.

Your sin is listed at #9.

Mayest

Answer 4

Just wrote some attached properties that should make it easy to set an individual Margin value from a binding or static resource:

public class Margin
{
    public static readonly DependencyProperty LeftProperty = DependencyProperty.RegisterAttached(
        "Left",
        typeof(double),
        typeof(Margin),
        new PropertyMetadata(0.0));

    public static void SetLeft(UIElement element, double value)
    {
        var frameworkElement = element as FrameworkElement;
        if (frameworkElement != null)
        {
            Thickness currentMargin = frameworkElement.Margin;

            frameworkElement.Margin = new Thickness(value, currentMargin.Top, currentMargin.Right, currentMargin.Bottom);
        }
    }

    public static double GetLeft(UIElement element)
    {
        return 0;
    }

    public static readonly DependencyProperty TopProperty = DependencyProperty.RegisterAttached(
        "Top",
        typeof(double),
        typeof(Margin),
        new PropertyMetadata(0.0));

    public static void SetTop(UIElement element, double value)
    {
        var frameworkElement = element as FrameworkElement;
        if (frameworkElement != null)
        {
            Thickness currentMargin = frameworkElement.Margin;

            frameworkElement.Margin = new Thickness(currentMargin.Left, value, currentMargin.Right, currentMargin.Bottom);
        }
    }

    public static double GetTop(UIElement element)
    {
        return 0;
    }

    public static readonly DependencyProperty RightProperty = DependencyProperty.RegisterAttached(
        "Right",
        typeof(double),
        typeof(Margin),
        new PropertyMetadata(0.0));

    public static void SetRight(UIElement element, double value)
    {
        var frameworkElement = element as FrameworkElement;
        if (frameworkElement != null)
        {
            Thickness currentMargin = frameworkElement.Margin;

            frameworkElement.Margin = new Thickness(currentMargin.Left, currentMargin.Top, value, currentMargin.Bottom);
        }
    }

    public static double GetRight(UIElement element)
    {
        return 0;
    }

    public static readonly DependencyProperty BottomProperty = DependencyProperty.RegisterAttached(
        "Bottom",
        typeof(double),
        typeof(Margin),
        new PropertyMetadata(0.0));

    public static void SetBottom(UIElement element, double value)
    {
        var frameworkElement = element as FrameworkElement;
        if (frameworkElement != null)
        {
            Thickness currentMargin = frameworkElement.Margin;

            frameworkElement.Margin = new Thickness(currentMargin.Left, currentMargin.Top, currentMargin.Right, value);
        }
    }

    public static double GetBottom(UIElement element)
    {
        return 0;
    }
}

Usage:

<TextBlock Text="Test"
    app:Margin.Top="{Binding MyValue}"
    app:Margin.Right="{StaticResource MyResource}"
    app:Margin.Bottom="20" />

Tested in UWP but this should work for any XAML-based framework. The nice thing is they won't override the other values on the Margin, so you can combine them as well.

Loiseloiter

I have ported your awesome answer to Xamarin: #55704960 – Dumond

Why are all the getters returning 0 ? – Liddie

The attached property system requires getters, but the system does not read them. Also if you need to get a margin from code you can use the built-in Margin property and not the attached property. You could implement the getters to return a correct value if you had a use case for it. – Loiseloiter

Answer 5

You can't define just the Top margin with a binding, because Margin is of type Thickness which isn't a dependency object. However you could use a MultiValueConverter that would take 4 margin values to make 1 Thickness objects

Converter :

public class ThicknessMultiConverter : IMultiValueConverter
{
    #region IMultiValueConverter Members

    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        double left = System.Convert.ToDouble(values[0]);
        double top = System.Convert.ToDouble(values[1]);
        double right = System.Convert.ToDouble(values[2]);
        double bottom = System.Convert.ToDouble(values[3]);
        return new Thickness(left, top, right, bottom);
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        Thickness thickness = (Thickness)value;
        return new object[]
        {
            thickness.Left,
            thickness.Top,
            thickness.Right,
            thickness.Bottom
        };
    }

    #endregion
}

XAML :

<StackPanel>
    <StackPanel.Margin>
        <MultiBinding Converter="{StaticResource myThicknessConverter}">
            <Binding Path="LeftMargin"/>
            <Binding Path="TopMargin"/>
            <Binding Path="RightMargin"/>
            <Binding Path="BottomMargin"/>
        </MultiBinding>
    </StackPanel.Margin>
</StackPanel>

Georas

How would this work considering he wants to set a single part of the margin and leave the other existing values intact? – Onyx

Well, all properties will have be set at initialisation, but afterwards you just have to change one of the bound properties... – Georas

BTW, your solution has exactly the same limitation ;) – Georas

I know, but mine's less code. :-) OTOH, yours at least would rebind when any of the values changes... – Onyx

You could add a ConverterParameter to the MultiBinding to specify which values you want to set: for example ConverterParameter="Top,Right" would only require two bindings and return a thickness with only the top and right margin set. – Hexa

Yes, but not setting the other ones is equivalent to set them to 0 (see Kent's answer) – Georas

Answer 6

I thought You could use the property syntax, from MSDN:

      <object.Margin>
        <Thickness Top="{Binding Top}"/>
      </object.Margin>

Than you won't need any converter

But the Top is not DependancyProperty - back to converter

Outclass

U'll get "Cannot set read-only property 'System.Windows.Thickness.Top'" – Menken

Also, this will still overwrite the other values with the default zero. So if that's not the behavior you want, then this won't work even with a hard coded value. – Studnia

Answer 7

Here's a simple way of doing this without writing converters or hard-coding margin values. First, define the following in your Window (or other control) resources:

<Window.Resources>
    <!-- Define the default amount of space -->
    <system:Double x:Key="Space">10.0</system:Double>

    <!-- Border space around a control -->
    <Thickness
        x:Key="BorderSpace"
        Left="{StaticResource Space}"
        Top="{StaticResource Space}"
        Right="{StaticResource Space}"
        Bottom="{StaticResource Space}"
        />

    <!-- Space between controls that are positioned vertically -->
    <Thickness
        x:Key="TopSpace"
        Top="{StaticResource Space}"
        />
</Window.Resources>

Note that system is defined as xmlns:system="clr-namespace:System;assembly=mscorlib".

Now you can use these resources as follows:

<Grid
    Margin="{StaticResource BorderSpace}"
    >
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>

    <Button
        Grid.Row="0"
        Content="Button 1"
        />

    <Button
        Grid.Row="1"
        Content="Button 2"
        Margin="{StaticResource TopSpace}"
        />
</Grid>

Now if you want to change the default space between controls, you only need to change it in one place.

Philous

Answer 8

I use a ValueConverter bound to Margin (RelativeSource Self) and Parse the ConverterParameter, given as "top:123;left:456".

The Converter only overwrites Margins given by Parameter.

public class MarginConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (!(value is Thickness)) return new Thickness();

        Thickness retMargin = (Thickness) value;
        List<string> singleMargins = (parameter as string)?.Split(';').ToList() ?? new List<string>();

        singleMargins.ForEach(m => {
                                  switch (m.Split(':').ToList()[0].ToLower().Trim()) {
                                      case "left":
                                          retMargin.Left = double.Parse(m.Split(':').ToList()[1].Trim());
                                          break;
                                      case "top":
                                          retMargin.Top = double.Parse(m.Split(':').ToList()[1].Trim());
                                          break;
                                      case "right":
                                          retMargin.Right = double.Parse(m.Split(':').ToList()[1].Trim());
                                          break;
                                      case "bottom":
                                          retMargin.Bottom = double.Parse(m.Split(':').ToList()[1].Trim());
                                          break;
                                  }
                              }
            );
        return retMargin;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

xaml

<TextBlock Margin="{Binding RelativeSource={RelativeSource Self}, 
                    Path=Margin, 
                    Converter={StaticResource MarginConverter}, 
                    ConverterParameter='top:0'}" 
Style="{StaticResource Header}" 
Text="My Header" />

TextBlock would use the Margin given by Style except the Margin-Top, that will be overwritten with 0.

Have fun with it!

Hewes

Answer 9

Use a converter, the sample code below will convert the double you are binding to to a thickness. It will set the "Top" of the thickness to the bound field. You could optionally use a ConverterParameter to determine if you are binding to left, top, right, or bottom.

<StackPanel Margin="{Binding TopMargin, Converter={StaticResource MyThicknessConverter}">

.

public class ThicknessSingleValueConverter : IValueConverter
{
    override Convert(...)
    {
         return new Thickness(0, (double)object, 0, 0);
    }

    //etc...

Machinist

Answer 10

Here's a nifty solution:

        public class Nifty
    {
        private static double _tiny;
        private static double _small;
        private static double _medium;
        private static double _large;
        private static double _huge;
        private static bool _resourcesLoaded;

        #region Margins

        public static readonly DependencyProperty MarginProperty =
            DependencyProperty.RegisterAttached("Margin", typeof(string), typeof(Nifty),
                new PropertyMetadata(string.Empty,
                    new PropertyChangedCallback(OnMarginChanged)));

        public static Control GetMargin(DependencyObject d)
        {
            return (Control)d.GetValue(MarginProperty);
        }

        public static void SetMargin(DependencyObject d, string value)
        {
            d.SetValue(MarginProperty, value);
        }

        private static void OnMarginChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            FrameworkElement ctrl = d as FrameworkElement;
            if (ctrl == null)
                return;

            string Margin = (string)d.GetValue(MarginProperty);

            ctrl.Margin = ConvertToThickness(Margin);
        }

        private static Thickness ConvertToThickness(string Margin)
        {
            var result = new Thickness();

            if (!_resourcesLoaded)
            {
                _tiny = (double)Application.Current.FindResource("TinySpace");
                _small = (double)Application.Current.FindResource("SmallSpace");
                _medium = (double)Application.Current.FindResource("MediumSpace");
                _large = (double)Application.Current.FindResource("LargeSpace");
                _huge = (double)Application.Current.FindResource("HugeSpace");

                _resourcesLoaded = true;
            }

            result.Left = CharToThickness(Margin[0]);
            result.Top = CharToThickness(Margin[1]);
            result.Bottom = CharToThickness(Margin[2]);
            result.Right = CharToThickness(Margin[3]);

            return result;
        }


        private static double CharToThickness(char p)
        {
            switch (p)
            {
                case 't':
                case 'T':
                    return _tiny;
                case 's':
                case 'S':
                    return _small;
                case 'm':
                case 'M':
                    return _medium;
                case 'l':
                case 'L':
                    return _large;
                case 'h':
                case 'H':
                    return _huge;
                default:
                    return 0.0;
            }
        }

        #endregion

    }

If you add this code to your namespace and define the following sizes:

    <system:Double x:Key="TinySpace">2</system:Double>
<system:Double x:Key="SmallSpace">5</system:Double>
<system:Double x:Key="MediumSpace">10</system:Double>
<system:Double x:Key="LargeSpace">20</system:Double>
<system:Double x:Key="HugeSpace">20</system:Double>

You can then create Tiny, Small, Medium, Large & Huge margins like this:

local:Nifty.Margin="H000"

or

local:Nifty.Margin="_S_S"

The code will then create margins based on your resources.

Halfpenny

Answer 11

Maybe I am "late to the party", but didn't like any of provided solutions, and it seems to me that simplest and cleanest solution is define Thickness property in ViewModel (or anything that you are binding) and then Bind that property. Something like this:

public class ItemViewModel
{
  public Thickness Margin { get; private set }

  public ItemViewModel(ModelClass model)
  {
    /// You can calculate needed margin here, 
    /// probably depending on some value from the Model
    this.Margin = new Thickness(0,model.TopMargin,0,0);
  }
}

And then XAML is simple:

<StackPanel Margin="{Binding Margin}">

Fairyfairyland

Thickness and margin are view-related concepts. As such, they don't belong in a proper view model. – Heisel

Answer 12

What would be nice is to be able to do this by specifying something like the code example below.

<StackPanel Margin=",10,,">

Unfortunately this capability doesn't seem to exist by default in WPF and it's a shame because it requires developers to hard code known default values in a way that later makes it more difficult to skin or theme an application.

The best solution that I can think of at this point is using a converter, but the amount of extra code you have to produce to introduce this is not ideal.

Antagonistic