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ASP.NET: Append client side functions with Attributes.Add
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Summary: The Attributes.Add method can be used to add and append client side functions.
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NOTE: This article applies only to HTML controls. ASP.NET controls do not exhibit this behaviour.
Say, for example, we had a HTML control that already had a javascript function attached to it's onblur event e.g.
- <input id="Text1" type="text" onblur="alert('Existing Function');" runat="server" />
If we used the Attributes.Add method to add another function, when we visit the page, the first function will have been replaced by our second. Try adding this and see the results:
- Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
- Text1.Attributes.Add("onblur", "alert('New Function');")
- End Sub
Notice how we only get an alert for the "New Function"? To combat this, we must append the exisiting functions as well e.g.
- Text1.Attributes.Add("onblur", "alert('New Function');" & Text1.Attributes.Item("onblur"))
This Hack is part of the ASP.NET Hacks collection
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