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, Jul 27 '10 at 06:41
Somehow each time I have a question someone had the exactly same question previously :) Great! — Ignacio Soler Garcia, Mar 24 '12 at 09:29
A fourth way to do this would be to use this answer: http://stackoverflow.com/a/2552911/222134 — Johny Skovdal, May 31 '14 at 14:55

score 172 · Accepted Answer · edited Jul 27 '12 at 02:09

172

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 '12 at 02:09

Mitkins

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answered Jul 27 '10 at 07:34

Noldorin

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@tofutim That's because MultiBinding doesn't seem to have Resources. Use TextBlock.Resources instead... – Martin Hennings Jul 01 '11 at 10:04
6

Maybe you should add xmlns:sys="clr-namespace:System;assembly=mscorlib" to your solution ;-) – c0d3b34n Jul 07 '17 at 06:21

score 122 · Answer 2 · edited May 26 '22 at 11:59

122

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 '22 at 11:59

StayOnTarget

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answered Jul 14 '12 at 20:43

Anders Kaplan

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It's needed to define the namespace `sys` at the document head: ```xmlns:sys="clr-namespace:System;assembly=mscorlib"``` – Beauty Dec 13 '18 at 12:08

score 31 · Answer 3 · answered Jul 27 '10 at 07:37

31

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 '10 at 07:37

benPearce

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seems to pass DependencyProperty.UnsetValue – Josh Stribling Jul 10 '15 at 01:25
1

passes the string "123" instead of the integer or double that I intended in my case. – Marcel Gosselin Jun 11 '18 at 18:49
1

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](https://msdn.microsoft.com/en-us/library/system.windows.data.ivalueconverter.convert(v=vs.100).aspx) – benPearce Jun 14 '18 at 01:32

score 9 · Answer 4 · answered Jul 01 '15 at 09:54

9

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

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

answered Jul 01 '15 at 09:54

David Hollinshead

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

4 Answers4

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