Could not load file or assembly AjaxControlToolkit

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Could not load file or assembly 'AjaxControlToolkit, Version=1.0.10920.32880, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Solution:
Option to Check:
AjaxControlToolkit dll has been not Properly Referenced or added

Option to check:
AjaxControlToolkit dll Namespaces has been Explicitly added in Page such as
below
asp:ScriptManager runat="server" ID="scrptMasterPage" ScriptMode="Release" EnablePageMethods="true" LoadScriptsBeforeUI="false"
CompositeScript ScriptMode="Release"
Scripts
asp:ScriptReference Name="MicrosoftAjax.js" asp:ScriptReference Name="MicrosoftAjaxWebForms.js"
asp:ScriptReference Name="AjaxControlToolkit.Compat.Timer.Timer.js" Assembly="AjaxControlToolkit, Version=1.0.10920.32880, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"
asp:ScriptReference Name="AjaxControlToolkit.Common.Common.js" Assembly="AjaxControlToolkit, Version=1.0.10920.32880, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"
asp:ScriptReference Name="AjaxControlToolkit.Animation.Animations.js" Assembly="AjaxControlToolkit, Version=1.0.10920.32880, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"
asp:ScriptReference Name="AjaxControlToolkit.ExtenderBase.BaseScripts.js" Assembly="AjaxControlToolkit, Version=1.0.10920.32880, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"
asp:ScriptReference Name="AjaxControlToolkit.CollapsiblePanel.CollapsiblePanelBehavior.js"
Assembly="AjaxControlToolkit, Version=1.0.10920.32880, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"
Scripts
CompositeScript
asp:ScriptManager