I am using autocomplete box and when i am typing the letters in am getting the javascript error, but when i am using the same datasource (data table) and compoent inside the radwindow it works fine.
UI:
<telerik:RadAutoCompleteBox RenderMode="Lightweight" ID="rad_txtTo" runat="server" InputType="Token" EmptyMessage="Select Contacts" Width="95%" DropDownPosition="Automatic"> </telerik:RadAutoCompleteBox>
Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:11507 Uncaught TypeError: Cannot read property 'left' of undefined
at c.DropDown._getDropDownHorizontalOffset (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:11507)
at c.DropDown.position (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:11406)
at c.DropDown._onDropDownReflowed (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:11467)
at b.DropDown.trigger (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:1789)
at b.DropDown.reflow (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:10232)
at b.DropDown.show (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:10151)
at c.DropDown.open (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:11404)
at c.RadAutoCompleteBox._populateDropDown (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:10963)
at c.RadAutoCompleteBox._onCallbackResponse (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bTelerik.Web.UI%2c+Version%3d2016.2.504.45%2c+Culture%3dneutral%2c+PublicKeyToken%3d121fae78165ba3d4%3aen-US%3a90ca7d67-b00e-437e-ad14-27cf2faf3a32%3a16e4e7cd%3af7645509%3a24ee1bba%3ac128760b%3a874f8ea2%3ab2e06756%3af46195d3%3a92fe8ea0%3afa31b949%3a4877f69a%3a33715776%3a19620875%3a490a9d4e%3abd8f85e4%3ab7778d6c%3ae085fe68%3aed16cbdc%3a1e771326%3a88144a7a%3a78b9daca%3a6d43f6d9%3a8674cba1%3a7c926187%3ac08e9f8a%3a59462f1%3aa51ee93e%3a58366029:10855)
at Object.eventCallback (Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=ctl00_rsmDefaultSiteMaster_TSM&compress=2&_TSM_CombinedScripts_=%3b%3bSystem.Web.Extensions%2c+Version%3d4.0.0.0%2c+Culture%3dneutral%2c+PublicKeyToken%3d31bf3856ad364e35%3aen-US%3a0506169f-fccc-46f8-a5ec-5e7be35dfbdd%3aea597d4b%3ab25378d2:6)