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c#wpfxamlbinding
Michel Keijzers
Michel Keijzers

Reputation: 15377

What is the use of Path= in XAML?

I use a lot of bindings in XAML and sometimes I use path= in a binding and sometimes not. In which cases do I need the path= and when can I omit this?

Upvotes: 24

Views: 19477

Answers (5)

Phil
Phil

Reputation: 43021

This is due to the fact that the Binding class has a default constructor, used when you have bindings like {Binding FallbackValue='HelloWorld', Path=MyProperty} and a constructor that has a single argument Path.

So when there is a list of property/value pairs the binding is created as

new Binding(){
  Path="MyProperty"
  ElementName="MyElement"
}

The second form is used for bindings like {Binding MyProperty, ...}. In this case the binding is created as

new Binding("MyProperty"){
  ElementName = "MyElement",
  ...
}

It's always correct (and possibly more correct) to specify Path=, but you can get away without it.

Upvotes: 12

Richard Szalay
Richard Szalay

Reputation: 84824

It can always be omitted as it's the default property of the Binding XAML extension. It's only specified explicitly for clarity when multiple properties are used.

Upvotes: 15

Natxo
Natxo

Reputation: 2947

Path is used to specify the name of the property of the underlying object to bind to.

When you bind to the DataContext, you can omit Path:

{Binding MyProperty}    

{Binding Path=MyProperty}

When you need to specify a source other than the DataContext you can use Source, RelativeSource, or ElementName to refer to the object, so you will usually have to specify to which property of it you want to set your binding:

<Button Background="{Binding ElementName=refButton, Path=Background}"/>

<TextBlock Width="{Binding RelativeSource={RelativeSource Self}, Path=Parent.ActualWidth}"/>

Upvotes: 7

rekire
rekire

Reputation: 47995

Like Richard Szalay said, it is optional if it is the first property. But in my opionion it is easier to read if you enter the path property. Also the code highlighting looks better.

Upvotes: 3

Jehof
Jehof

Reputation: 35564

You can always omit the Path= when you write the path to the property directly behind the Binding statement.

{Binding MyProperty}

is the same as

{Binding Path=MyProperty}

When you inline the path to the property you need to specify it with Path=

{Binding FallbackValue='HelloWorld', Path=MyProperty}

Upvotes: 4

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