Today I ran into this error when posting back on my ASP.NET page.

System.Web.HttpUnhandledException (0x80004005): Exception of type ‘System.Web.HttpUnhandledException’ was thrown. —> System.ArgumentException: Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation=”true”/> in configuration or <%@ Page EnableEventValidation=”true” %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.
at System.Web.UI.ClientScriptManager.ValidateEvent(String uniqueId, String argument)

It did not take me long to track down the problem. I forgot to add an ID to a dynamically created dropdownlist control.

 

Error:

An exception of type ‘System.MissingMethodException’ occurred in mscorlib.dll but was not handled in user code

Additional information: No parameterless constructor defined for this object.

 

Possible Solution:

If defining your gridview’s data source in the ASP.NET markup. Make sure the code behind’s constructor is public and has the right visibility.

In my case, Resharper suggested making the constructor protected, which this problem.

I just ran into this error when upgrading a OsCommerce Site:

Fatal error: Call to a member function buildBlocks() on a non-object in public_html/includes/template_top.php on line 13

I saw that others had this error, but no one was able to help them. In case anyone else runs into this error check the following:

In catalog/includes/application_top.php you want to make sure you instantiate oscTemplate.

@@ -420,6 +420,9 @@
require(DIR_WS_FUNCTIONS . 'specials.php');
tep_expire_specials();

+ require(DIR_WS_CLASSES . 'osc_template.php');
+ $oscTemplate = new oscTemplate();
+

// calculate category path
if (isset($HTTP_GET_VARS['cPath'])) {
$cPath = $HTTP_GET_VARS['cPath'];

This code snippet comes from the OsCommerce V2.2RC2a to V2.3 Upgrade guide found here