Can't Get Style RSS

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  leabre

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  Can't Get Style

  May 21, 2003 04:07 PM|LINK

  Greets, When I inherit from WebControl and place the control wherever I want in the IDE (in Grid layout) all is well. When I view that page in a browser, however, the control is always at the top left corner of the screen. I'm presume it's because I'm not setting the "style" to appropriately reflect absolute positioning and the top and left coordinates. Saying "left = Style["left"] doesn't return anything and I don't see any other properties or methods that provide this functionality. The WebControl itself doesn't appear to provide this functionality, either. How to I get those cordinates from the IDE so I can write them in the final HTML stream to be rendered? Thanks, Shawn
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  Craig Guttor...

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  Re: Can't Get Style

  May 21, 2003 05:48 PM|LINK

  Are you perhaps overriding AddAttributesToRender() ? That's where the style="position: absolute...." would be added. If you are overriding it, you can always add:

  MyBase.AddAttributesToRender(writer)

  Craig Guttormson, MCP
  
  
  
  
  
  -- This behaviour is by design.
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  leabre

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  Re: Can't Get Style

  May 21, 2003 08:09 PM|LINK

  Will this cause the left and top styles to be rendered correctly as they are positioned in the IDE? I will have to look into this later I'm not near that project at the moment... but if it will cause those styles to be rendered then that's just dandy... =)) Thanks, Shawn
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  joteke

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  Re: Can't Get Style

  May 21, 2003 09:03 PM|LINK

  Yes, it renders all HTML and style attributes that need to be rendered by the control. By default WebControl implements this in RenderBeginTag method:

  public virtual void RenderBegintag(HtmlTextWriter writer)
  {
     AddAttributesToRender(writer)
     HtmlTextWriterTag tagKey=TagKey;
     ...
  }

  So by overriding AddAttributesToRender of the WebControl, you can customize what attributes it will output. Call to base class's version ensures that design-time placing works and it is reflected in the rendering.
  Thanks,
  
  Teemu Keiski
  Finland, EU
  
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  leabre

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  Re: Can't Get Style

  May 21, 2003 09:26 PM|LINK

  Okay, what you say makes sense but I must be missing something here... when I create a new webcontrol and override addattributestorender... the output doesn't add the stream nor is it accessible without throwing an exception... ")> Public Class TestControl Inherits System.Web.UI.WebControls.WebControl Dim _text As String Property [Text]() As String Get Return _text End Get Set(ByVal Value As String) _text = Value End Set End Property Protected Overrides Sub AddAttributesToRender(ByVal writer As HtmlTextWriter) writer.AddStyleAttribute("position", "absolute") MyBase.AddAttributesToRender(writer) End Sub Protected Overrides Sub Render(ByVal output As System.Web.UI.HtmlTextWriter) 'output.Write(MyBase.Style.Item("position").ToString) ' Fails output.Write([Text]) End Sub End Class So I must be missing something here because it's still rendering in the top left no matter where it's positioned... now, in reality, the control in question (that I'm working on) will be rendering a table that needs to be positioned. Any ideas? Thanks, Shawn
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  joteke

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  Re: Can't Get Style

  May 21, 2003 09:31 PM|LINK

  Hi, remove the overridden AddAttributesToRender and Render methods completely from the control as by default they should work just fine for your control's purposes. Instead override the RenderContents method of your control:

  Protected Overrides Sub RenderContents(ByVal output As System.Web.UI.HtmlTextWriter)
  output.Write([Text])
  End Sub

  Idea is that RenderContents is called when your control want's to Render it's contents (Text/markup it contains).
  Thanks,
  
  Teemu Keiski
  Finland, EU
  
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  leabre

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  Re: Can't Get Style

  May 21, 2003 09:45 PM|LINK

  Great, That worked (after I removed Render)... it places a .. tag around whatever is rendered to the screen. Lets take this one step further (if you don't mind?)... when I place a TextBox control on a form it renders <input ... style='left:....".... etc... and doesn't wrap it in a span. My control will ultimately be rendered in a ... how would I go about causing such a behavior... PS: thanks for your help thus far, I've been stuck for a very long time on this. Thanks, Shawn
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  joteke

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  Re: Can't Get Style

  May 21, 2003 10:04 PM|LINK

  Yes, correct. That is because by default WebControl renders SPAN tag. Say if you'd like to write out an table with one row and cell where the text resides. Quickly thinking you'd have three options for doing it. 1) Set the TagKey property of your control to point the "main" tag that the control is rendered as. Render the contents in RenderContents method. Example:

  Imports System
  Imports System.ComponentModel
  Imports System.Web.UI
  Imports System.Web.UI.WebControls
  
  
  ")> Public Class TestControl
      Inherits System.Web.UI.WebControls.WebControl, INamingContainer
  
  
      Dim _text As String
  
  
       Property [Text]() As String
          Get
              Return _text
          End Get
  
  
          Set(ByVal Value As String)
              _text = Value
          End Set
      End Property
  
  
  
  
      Protected Overrides ReadOnly Property TagKey() As System.Web.UI.HtmlTextWriterTag
          Get
              Return HtmlTextWriterTag.Table
          End Get
      End Property
  
  
  
  
      Protected Overrides Sub RenderContents(ByVal writer As System.Web.UI.HtmlTextWriter)
          writer.RenderBeginTag(HtmlTextWriterTag.Tr)
          writer.RenderBeginTag(HtmlTextWriterTag.Td)
          writer.Write(Text)
          writer.RenderEndTag()
          writer.RenderEndTag()
      End Sub
  End Class

  2. Write it all out in Render method. This would mean applying AddAttributesToRender (because if we'd call base class's implementation, we would get the also). Example: Example:

  Imports System
  Imports System.ComponentModel
  Imports System.Web.UI
  Imports System.Web.UI.WebControls
  
  ")> Public Class TestControl
      Inherits System.Web.UI.WebControls.WebControl
  
      Dim _text As String
  
       Property [Text]() As String
          Get
              Return _text
          End Get
  
          Set(ByVal Value As String)
              _text = Value
          End Set
      End Property
  
  
      Protected Overrides Sub Render(ByVal writer As System.Web.UI.HtmlTextWriter)
          AddAttributesToRender(writer)
          writer.RenderBeginTag(HtmlTextWriterTag.Table)
          writer.RenderBeginTag(HtmlTextWriterTag.Tr)
          writer.RenderBeginTag(HtmlTextWriterTag.Td)
          writer.Write(Text)
          writer.RenderEndTag()
          writer.RenderEndTag()
          writer.RenderEndTag()
      End Sub
  End Class
  
  

  3) Create your control as composite control, and create the table by adding corresponding controls (Table,TableRow,TableCell) into your control's child controls and render them out in Render method of your control. Example:

  Imports System
  Imports System.ComponentModel
  Imports System.Web.UI
  Imports System.Web.UI.WebControls
  
  ")> Public Class TestControl
      Inherits System.Web.UI.WebControls.WebControl
  
      Dim _text As String
  
       Property [Text]() As String
          Get
              Return _text
          End Get
  
          Set(ByVal Value As String)
              _text = Value
          End Set
      End Property
  
      Protected Overrides Sub CreateChildControls()
          Dim t As New Table
          Controls.Add(t)
          Dim tr As New TableRow
          Dim td As New TableCell
          td.Text = Text
          tr.Cells.Add(td)
          t.Rows.Add(tr)
      End Sub
  
      Protected Overrides Sub Render(ByVal writer As System.Web.UI.HtmlTextWriter)
          AddAttributesToRender(writer)
          RenderChildren(writer)
      End Sub
  End Class
  
  

  Composition might seem the easiest way to do the task, but it is also the less performatic, because it includes the extra control creation, state management and so on.
  Thanks,
  
  Teemu Keiski
  Finland, EU
  
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  leabre

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  Re: Can't Get Style

  May 21, 2003 10:11 PM|LINK

  Good reply, I'll see what I can do... you've been helpful... thanks... just one more question... In all of this process (as long as it works I'll be happy -- and it looks to be the solution)... is there a way I can (in the source code of my webcontrol) access the what the top and left and some other style properties that will eventually be written into the html writer? Or is it that I can't know but somehow (as you described above) it'll just get rendered in the end? Thanks, Shawn
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  joteke

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  Re: Can't Get Style

  May 21, 2003 10:17 PM|LINK

  Ah, yes that is the task of the AddAttributesToRender method. It will output automatically those that are applied to WebControl (via properties/styles of the control) and also if you put there custom attributes (so-called expando attributes) that are outputted as well. For example moving the WebControl in the design view has impact on this (it effects top/left styles). So if you meant how to have effect on these on the control itself, modify control's proeprties as you find the best. And you could add your own attributes in the AddAttributesToRender method if you override it (like you did in your first example).
  Thanks,
  
  Teemu Keiski
  Finland, EU