[Mono-bugs] [Bug 53898][Blo] New - System.ComponentModel.AttributeCollection:GetDefaultAttribute throws MissingMethodException

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Changed by jonwagner@hotmail.com.

http://bugzilla.ximian.com/show_bug.cgi?id=53898

--- shadow/53898	2004-02-04 18:22:13.000000000 -0500
+++ shadow/53898.tmp.18277	2004-02-04 18:22:13.000000000 -0500
@@ -0,0 +1,96 @@
+Bug#: 53898
+Product: Mono/Class Libraries
+Version: unspecified
+OS: Red Hat 9.0
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: Unknown
+Priority: Blocker
+Component: System
+AssignedTo: mono-bugs@ximian.com                            
+ReportedBy: jonwagner@hotmail.com               
+QAContact: mono-bugs@ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: System.ComponentModel.AttributeCollection:GetDefaultAttribute throws MissingMethodException
+
+Please fill in this template when reporting a bug, unless you know what 
+you are doing.
+Description of Problem:
+
+System.ComponentModel.AttributeCollection:GetDefaultAttribute throws an 
+System.MissingMethodException. Stack trace follows.
+
+
+Steps to reproduce the problem:
+1. Not exactly sure - but I have custom validators in an aspx file. 
+During page render, the exception below is thrown.
+
+Actual Results:
+System.MissingMethodException: Default constructor not foundin <0x00144> 
+System.Activator:CreateInstance (System.Type,bool)in <0x00012> 
+System.Activator:CreateInstance (System.Type)in <0x00046> 
+System.ComponentModel.AttributeCollection:GetDefaultAttribute 
+(System.Type)in <0x00129> 
+System.ComponentModel.AttributeCollection:get_Item (System.Type)in 
+<0x00039> System.Web.UI.WebControls.BaseValidator:GetValidationProperty 
+(object)in <0x00082> 
+System.Web.UI.WebControls.BaseValidator:CheckControlValidationProperty 
+(string,string)in <0x00093> 
+System.Web.UI.WebControls.BaseValidator:ControlPropertiesValid ()in 
+<0x00021> System.Web.UI.WebControls.BaseValidator:get_PropertiesValid ()
+in <0x0009a> System.Web.UI.WebControls.BaseValidator:Render 
+(System.Web.UI.HtmlTextWriter)in <0x0001c> 
+System.Web.UI.Control:RenderControl (System.Web.UI.HtmlTextWriter)in 
+<0x00209> ASP.Logon_ascx:__Render_LogonPane 
+(System.Web.UI.HtmlTextWriter,System.Web.UI.Control)in <0x0005a> (wrapper 
+delegate-invoke) 
+System.MulticastDelegate:invoke_void_HtmlTextWriter_Control 
+(System.Web.UI.HtmlTextWriter,System.Web.UI.Control)in <0x00049> 
+System.Web.UI.Control:RenderChildren (System.Web.UI.HtmlTextWriter)
+
+Expected Results:
+Shouldn't throw an exception.
+
+How often does this happen? 
+Any time a page with the control is hit.
+
+
+Additional Information:
+I'm just getting started with bugzilla/cvs/etc, so please be patient.
+
+The problem is called by a bad implementation of 
+System.ComponentModel.AttributeCollection:GetDefaultAttribute throws 
+MissingMethodException. It assumes that the attribute has a default 
+constructor, and not all attributes do.
+
+Here's a replacement GetDefaultAttribute (I don't have my system set up 
+for patching yet, but I promise for the next bug.) that uses 
+GetConstructor with a check rather than an exception.
+
+		protected Attribute GetDefaultAttribute (Type 
+attributeType)
+		{
+			Attribute attr = null;
+			BindingFlags bf = BindingFlags.Public | 
+BindingFlags.Static;
+
+			FieldInfo def = attributeType.GetField 
+("Default", bf);
+			if (def == null) {
+				ConstructorInfo constructorInfo = 
+attributeType.GetConstructor (new Type[0]);
+				if (constructorInfo != null)
+					attr = (Attribute)
+constructorInfo.Invoke (new Object[0]);
+				if (attr != null && !
+attr.IsDefaultAttribute ())
+					attr = null;
+			} else {
+				attr = (Attribute) def.GetValue (null);
+			}
+
+			return attr;
+		}