How can I pass a constant value for 1 binding in multi-binding?

Question

I have a multi-binding like

<TextBlock>
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource myConverter}">
            <Binding Path="myFirst.Value" />
            <Binding Path="mySecond.Value" />
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

And I want to pass a fixed value e.g. "123" to one of the two bindings above. How can I do that using XAML?

I think some part of the question is missing, you are refering to binding above but I don't see any binding code in the question. — akjoshi
– akjoshi, Commented Jul 27, 2010 at 6:41
Somehow each time I have a question someone had the exactly same question previously :) Great! — Ignacio Soler Garcia
– Ignacio Soler Garcia, Commented Mar 24, 2012 at 9:29
A fourth way to do this would be to use this answer: stackoverflow.com/a/2552911/222134 — Johny Skovdal
– Johny Skovdal, Commented May 31, 2014 at 14:55

Mitkins · Accepted Answer · 2012-07-27 02:09:34Z

180

If your value is simply a string, you can specify it as a constant in the Source property of a binding. If it is any other primitive data type, you need to define a static resource and reference this.

Define the sys namespace in the root of the XAML to point to System in mscorlib, and the following should work:

<TextBlock>
  <TextBlock.Resources>
    <sys:Int32 x:Key="fixedValue">123</sys:Int32>
  </TextBlock.Resources>
  <TextBlock.Text>
    <MultiBinding Converter="{StaticResource myConverter}">
      <Binding Path="myFirst.Value" />
      <Binding Source="{StaticResource fixedValue}" />
    </MultiBinding>
  </TextBlock.Text>
</TextBlock>

edited Jul 27, 2012 at 2:09

Mitkins

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answered Jul 27, 2010 at 7:34

Noldorin

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3 Comments

Martin Hennings Over a year ago

@tofutim That's because MultiBinding doesn't seem to have Resources. Use TextBlock.Resources instead...

c0d3b34n Over a year ago

Maybe you should add xmlns:sys="clr-namespace:System;assembly=mscorlib" to your solution ;-)

thomasgalliker Dec 23, 2024 at 6:54

This code even works in 2024 with .NET MAUI :-) Thanks!

StayOnTarget · Accepted Answer · 2022-05-26 11:59:38Z

127

Or, combining the two answers above:

Define the namespace sys at the document head:

xmlns:sys="clr-namespace:System;assembly=mscorlib"

and then:

<MultiBinding Converter="{StaticResource ScalingConverter}">
    <Binding>
        <Binding.Source>
            <sys:Double>0.5</sys:Double>
        </Binding.Source>
    </Binding>
    <Binding ElementName="TC" Path="ActualWidth" />
</MultiBinding>

Which provides the right type without the Resources kludge.

edited May 26, 2022 at 11:59

StayOnTarget

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answered Jul 14, 2012 at 20:43

Anders Kaplan

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1 Comment

Beauty Over a year ago

It's needed to define the namespace sys at the document head: xmlns:sys="clr-namespace:System;assembly=mscorlib"

benPearce · Accepted Answer · 2010-07-27 07:37:18Z

33

I don't quite follow the question but there are two options:

Put the line <Binding Source="123" /> in your multibinding will pass 123 as a bound value to your converter.

Put ConverterParameter="123" in your MultiBinding:

<MultiBinding Converter="{StaticResource conv}" ConverterParameter="123">

answered Jul 27, 2010 at 7:37

benPearce

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3 Comments

Josh Stribling Over a year ago

<Binding Source="123" /> seems to pass DependencyProperty.UnsetValue

Marcel Gosselin Over a year ago

<Binding Source="123" /> passes the string "123" instead of the integer or double that I intended in my case.

benPearce Over a year ago

In IValueConverter, the parameters are passed as object, which means you would need cast the value to the correct type, in a safe way. IValueConverter.Convert

David Hollinshead · Accepted Answer · 2015-07-01 09:54:52Z

9

I'm not saying this an especially good answer but here is another approach:

<Binding Path="DoesNotExist" FallbackValue="123" />

answered Jul 1, 2015 at 9:54

David Hollinshead

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