/// <summary>
/// Will add an error to model state for a key if that key and error don't already exist
/// </summary>
/// <param name="modelState"></param>
/// <param name="key"></param>
/// <param name="errorMsg"></param>
/// <returns></returns>
private static bool TryAddModelError(this System.Web.Http.ModelBinding.ModelStateDictionary modelState, string key, string errorMsg)
{
if (modelState.TryGetValue(key, out var errs))
{
foreach (var e in errs.Errors)
{
if (e.ErrorMessage == errorMsg)
{
return(false); //if this same error message exists for the same key, just exit
}
}
}
modelState.AddModelError(key, errorMsg);
return(true);
}