In WPF what are the differences between the x Name and Name attributes

Question

Sometimes it seems that the Name and x Name attributes are interchangeable  So  what are the definitive differences between them  and when is it preferable to use one over the other  Are there any performance or memory implications to using them the wrong way

User · Accepted Answer

There really is only one name in XAML  the x Name  A framework  such as WPF  can optionally map one of its properties to XAML s x Name by using the RuntimeNamePropertyAttribute on the class that designates one of the classes properties as mapping to the x Name attribute of XAML   The reason this was done was to allow for frameworks that already have a concept of  Name  at runtime  such as WPF  In WPF  for example  FrameworkElement introduces a Name property   In general  a class does not need to store the name for x Name to be useable  All x Name means to XAML is generate a field to store the value in the code behind class  What the runtime does with that mapping is framework dependent   So  why are there two ways to do the same thing  The simple answer is because there are two concepts mapped onto one property  WPF wants the name of an element preserved at runtime  which is usable through Bind  among other things  and XAML needs to know what elements you want to be accessible by fields in the code behind class  WPF ties these two together by marking the Name property as an alias of x Name   In the future  XAML will have more uses for x Name  such as allowing you to set properties by referring to other objects by name  but in 3 5 and prior  it is only used to create fields   Whether you should use one or the other is really a style question  not a technical one  I will leave that to others for a recommendation   See also AutomationProperties Name VS x Name  AutomationProperties Name is used by accessibility tools and some testing tools

User · Answer

Name    can be used only for descendants of FrameworkElement and FrameworkContentElement  can be set from code-behind via SetValue   and property-like    x Name    can be used for almost all XAML elements  can NOT be set from code-behind via SetValue    it can only be set using attribute syntax on objects because it is a directive    Using both directives in XAML for one FrameworkElement or FrameworkContentElement will cause an exception  if the XAML is markup compiled  the exception will occur on the markup compile  otherwise it occurs on load

User · Answer

I always use the x Name variant  I have no idea if this affects any performance  I just find it easier for the following reason  If you have your own usercontrols that reside in another assembly just the  Name  property won t always suffice  This makes it easier to just stick too the x Name property

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X Name can cause memory issues if you have custom controls   It will keep a memory location for the NameScope entry     I say never use x Name unless you have to

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They are not the same thing   x Name is a xaml concept  used mainly to reference elements  When you give an element the x Name xaml attribute   the specified x Name becomes the name of a field that is created in the underlying code when xaml is processed  and that field holds a reference to the object    MSDN  So  it s a designer-generated field  which has internal access by default   Name is the existing string property of a FrameworkElement  listed as any other wpf element property in the form of a xaml attribute   As a consequence  this also means x Name can be used on a wider range of objects  This is a technique to enable anything in xaml to be referenced by a given name

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My research is x Name as global variable  However  Name as local variable  Does that mean x Name you can call it anywhere in your XAML file but Name is not  Example    lt StackPanel gt   lt TextBlock Text   Binding Path Content  ElementName btn     gt   lt Button Content  Example  Name  btn    gt   lt  StackPanel gt   lt TextBlock Text   Binding Path Content  ElementName btn     gt    You can t Binding property Content of Button with Name is  btn  because it outside StackPanel

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When you declare a Button element in XAML you are referring to a class defined in windows run time called Button   Button has many attribute such as background  text  margin        and an attribute called Name   Now when you declare a Button in XAML is like creating an anonymous object that happened to have an attribute called Name   In general you can not refer to an anonymous object  but in WPF framework XAML processor enables you to refer to that object by whatever value you have given to Name attribute   So far so good   Another way to create an object is create a named object instead of anonymous object  In this case XAML namespace has an attribute for an object called Name  and since it is in XAML name space thus have X   that you may set so you can identify your object and refer to it   Conclusion   Name is an attribute of a specific object  but X Name is one attribute of that object  there is a class that defines a general object

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It s not a WPF item but a standard XML one and BtBh has correctly answered it  x refers to the default namespace  In XML when you do not prefix an element attribute with a namespace it assumes you want the default namespace  So typing just Name is nothing more than a short hand for x Name  More details on XML namespaces can be found at link text

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One of the answers is that x name is to be used inside different program languages such as c  and name is to be used for the framework  Honestly that is what it sounds like to me

User · Answer

x Name and Name are referencing different namespaces    x name is a reference to the x namespace defined by default at the top of the Xaml file   xmlns x  http   schemas microsoft com winfx 2006 xaml    Just saying Name uses the default below namespace    xmlns  http   schemas microsoft com winfx 2006 xaml presentation    x Name is saying use the namespace that has the x alias  x is the default and most people leave it but you can change it to whatever you like  xmlns foo  http   schemas microsoft com winfx 2006 xaml    so your reference would be foo name  Define and Use Namespaces in WPF    OK lets look at this a different way  Say you drag and drop an button onto your Xaml page  You can reference this 2 ways x name and name  All xmlns  http   schemas microsoft com winfx 2006 xaml presentation  and xmlns x  http   schemas microsoft com winfx 2006 xaml  are is references to multiple namespaces  Since xaml holds the Control namespace not 100  on that  and presentation holds the FrameworkElement AND the Button class has a inheritance pattern of    Button   ButtonBase ButtonBase   ContentControl  ICommandSource ContentControl   Control  IAddChild Control   FrameworkElement FrameworkElement   UIElement  IFrameworkInputElement                       IInputElement  ISupportInitialize  IHaveResources   So as one would expect anything that inherits from FrameworkElement would have access to all its public attributes  so in the case of Button it is getting its Name attribute from FrameworkElement  at the very top of the hierarchy tree   So you can say x Name or Name and they will both be accessing the getter setter from the FrameworkElement    MSDN Reference  WPF defines a CLR attribute that is consumed by XAML processors in order to map multiple CLR namespaces to a single XML namespace  The XmlnsDefinitionAttribute attribute is placed at the assembly level in the source code that produces the assembly  The WPF assembly source code uses this attribute to map the various common namespaces  such as System Windows and System Windows Controls  to the http   schemas microsoft com winfx 2006 xaml presentation namespace   So the assembly attributes will look something like   PresentationFramework dll - XmlnsDefinitionAttribute    assembly  XmlnsDefinition  http   schemas microsoft com winfx 2006 xaml presentation    System Windows      assembly  XmlnsDefinition  http   schemas microsoft com winfx 2006 xaml presentation    System Windows Data      assembly  XmlnsDefinition  http   schemas microsoft com winfx 2006 xaml presentation    System Windows Navigation      assembly  XmlnsDefinition  http   schemas microsoft com winfx 2006 xaml presentation    System Windows Shapes      assembly  XmlnsDefinition  http   schemas microsoft com winfx 2006 xaml presentation    System Windows Documents      assembly  XmlnsDefinition  http   schemas microsoft com winfx 2006 xaml presentation    System Windows Controls

User · Answer

The only difference is that if you are using user Controls into a control from Same Assembly then Name will not identify your control and you will get an error   Use x Name for controls in the same Assembly    So x Name is the WPF versioning of naming controls in WPF  Name is just used as a Winform Legacy  They wanted to differentiate the naming of controls in WPF and winforms as they use attributes in Xaml to identify controls from other assemblies they used x  for Names of control    Just keep in mind dont put a name for a control just for the sake of keeping it as it resides in memory as a blank and it will give you a warning that Name has been applied for a control buts its never used

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Name can also be set using property element syntax with inner text  but that is uncommon  In contrast  x Name cannot be set in XAML property element syntax  or in code using SetValue  it can only be set using attribute syntax on objects because it is a directive   If Name is available as a property on the class  Name and x Name can be used interchangeably as attributes  but a parse exception will result if both are specified on the same element  If the XAML is markup compiled  the exception will occur on the markup compile  otherwise it occurs on load

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x Name means  create a field in the code behind to hold a reference to this object   Name means  set the name property of this object

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They re both the same thing  a lot of framework elements expose a name property themselves  but for those that don t you can use x name - I usually just stick with x name because it works for everything   Controls can expose name themselves as a Dependency Property if they want to   because they need to use that Dependency Property internally   or they can choose not to    More details in msdn here and here      Some WPF framework-level applications   might be able to avoid any use of the   x Name attribute  because the Name   dependency property as specified   within the WPF namespace for several   of the important base classes such as   FrameworkElement FrameworkContentElement   satisfies this same purpose  There are   still some common XAML and framework   scenarios where code access to an   element with no Name property is   necessary  most notably in certain   animation and storyboard support   classes  For instance  you should   specify x Name on timelines and   transforms created in XAML  if you   intend to reference them from code       If Name is available as a property on   the class  Name and x Name can be used   interchangeably as attributes  but an   error will result if both are   specified on the same element

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The specified x Name becomes the name of a field that is created in the underlying code when XAML is processed  and that field holds a reference to the object  In Silverlight  using the managed API  the process of creating this field is performed by the MSBuild target steps  which also are responsible for joining the partial classes for a XAML file and its code-behind  This behavior is not necessarily XAML-language specified  it is the particular implementation that Silverlight applies to use x Name in its programming and application models   Read More on MSDN

[.net] In WPF, what are the differences between the x:Name and Name attributes?

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