I have recently been working with Visual Studio 2015 and the following error occurred when I inserted a component in the HTML code. I think it's a silly mistake for lack of knowledge, but I have no idea how to solve it.
You have been missing the tag prefix
Example:
<%@ Register assembly="DevExpress.Web.ASPxRichEdit.v17.1, Version=17.1.4.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" namespace="DevExpress.Web.ASPxRichEdit" tagprefix="dx" %>
<%@ Register assembly="DevExpress.Web.v17.1, Version=17.1.4.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" namespace="DevExpress.Web" tagprefix="dx" %>
Sources:
DevExpress: How to: Insert RTF text to a document
Addendum:
The following error appeared and I'm trying to fix it: To work properly, DevExpress components require ASPxHttpHandlerModule registered in the web.config file
According to the document reference, follow the instructions for
IIS (Classic Mode)
<system.web>
<httpHandlers>
<add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.v17.2, Version=17.2.5.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" verb="GET"
path="DX.ashx" validate="false" />
</httpHandlers>
<httpModules>
<add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.v17.2, Version=17.2.5.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" name="ASPxHttpHandlerModule"/>
</httpModules>
</system.web>
IIS (Integrated Mode)
<system.web>
<httpHandlers>
<add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.v17.2, Version=17.2.5.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" verb="GET"
path="DX.ashx" validate="false" />
</httpHandlers>
<httpModules>
<add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.v17.2, Version=17.2.5.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" name="ASPxHttpHandlerModule"/>
</httpModules>
</system.web>
<system.webServer>
<validation validateIntegratedModeConfiguration="false" />
<handlers>
<add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.v17.2, Version=17.2.5.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" verb="GET" name="ASPxHttpHandlerModule"
path="DX.ashx" preCondition="integratedMode" />
</handlers>
<modules>
<add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.v17.2, Version=17.2.5.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" name="ASPxHttpHandlerModule"/>
</modules>
</system.webServer>