Controller
ViewBag.Subdivison = new SelectList(db.Retention_Model_Predictions_DS_Manual.Select(m => m.Underwriter_Name).Distinct(), "Underwriter_Name", "Underwriter_Name");
View
@Html.DropDownList("Underwriter_Name", null, "Please Select", htmlAttributes: new { @class = "form-control" })
Error found in Controller
"Error = Unable to evaluate the expression. Operation not supported. Unknown error: 0x80070057."
Error found in view
There is no ViewData item of type 'IEnumerable' that has the key 'Underwriter_Name'.
I don't think
ViewBag.Subdivison = new SelectList(db.Retention_Model_Predictions_DS_Manual.Select(m => m.Underwriter_Name).Distinct(), "Underwriter_Name", "Underwriter_Name");
is the reason you're getting the error in your controller.
However, the error you're receiving in your view is because your ViewBag name is Subdivison
but yet you're calling Underwriter_Name
as the first parameter in your DropDownList method.
Change your View code to:
@Html.DropDownList("Subdivison", null, "Please Select", htmlAttributes: new { @class = "form-control" })
You spelled subdivison wrong.. you're missing an 'i'. Subdivision.
Hope this helps.