In visual studio, I had a drop down list whose data source was connected to a LINQ query. Because there are many records, the client ask for a searchable control. I have replaced the drop down list with MultipleLookupField in the ascx page in visual studio. How can I bind this control to a data source? Is it possible to show checkbox beside each records?
Did you create visual web part in SharePoint 2010, SharePoint 2013 or SharePoint 2016?
Per my test in my SharePoint 2013 environment, then I cannot find the SharePoint:MultipleLookupField control which can be added when creating visual web part.
You could add the control and bind the data source using C# code in code behind. There is a similar post: