The ValidationSummary helper method generates an unordered list (ul element) of validation messages that are in the ModelStateDictionary object.
The ValidationSummary can be used to display all the error messages for all the fields. It can also be used to display custom error messages. The following figure shows how ValidationSummary displays the error messages.
ValidationSummary() Signature
MvcHtmlStringValidateMessage(bool excludePropertyErrors, string message, object htmlAttributes)
Display field level error messages using ValidationSummary
By default, ValidationSummary filters out field level error messages. If you want to display field level error messages as a summary then specify excludePropertyErrors = false.
Example - ValidationSummary to display field errors
@Html.ValidationSummary(false, "", new { @class = "text-danger" })
So now, the following Edit view will display error messages as a summary at the top. Please make sure that you don't have a ValidationMessageFor method for each of the fields.