My case: It’s a standard register form created in a SharePoint WebPart (but this error could happen even if you’re not using SharePoint). When I submit the form, sometimes I loose the information of DropDowns (but not the information of textboxes) and it seems to happen randomly. I checked the packages sent with Wireshark and […]
Error Cannot have multiple items selected in a DropDownList Solution This message means that you're trying to select an item and another one is already selected. To solve this problem you've to clear the previous selection an then select the new one, like this: myDropDownList.ClearSelection(); myDropDownList.Items.FindByValue(myValue).Selected = true;