Display error even while Model.IsValid returns true - asp.net

Question

I'm making a website that pulls some information from a SQL DB.
I have made a Model for validating that i have the information i need before i try the query. This means (if things go right) the method will always resolve and the Model.IsValid will be true. The query is to get all rows between two given dates.
Now comes my problem - When it gets into the ActionResult where it calls the query i first want to check if the amount of rows returned is less than 1000.
If it is < 1000 i want it to show the view with the rows, however if it's greater than 1000 i want an error message to be displayed that tells the user to narrow the search criterias.
I might be going about this the complete wrong way, and my initial idea was to "simply" change the validator to no longer being valid. Which would the automatically trigger the error message from the model. After searching around though that doesn't seem to be a possibility.
Anyone got some ideas how to go about this? Am completely wrong about my approach?
ValidatorModel:
public class DateValidator
{
[Required]
public DateTime StartDateTime { get; set; }
[Required]
public DateTime EndDateTime { get; set; }
}
ActionResult:
public ActionResult GetListFromDateRange(DateValidator validator)
{
RangeParent parent = new RangeParent();
if (ModelState.IsValid)
{
int queryCount =
repository.GetCountFromDateRange(validator.StartDateTime,
validator.EndDateTime);
if (queryCount < 1000)
{
parent.Meters =
repository.GetListFromDateRange(validator.StartDateTime,
validator.EndDateTime);
return View(Constants.ViewNames.DisplayRangeData, parent);
}
else
{
//display error message telling user to narrow the datetime range
return new EmptyResult();
}
}
return View(Constants.ViewNames.IndexView);
}
And last the two queries i currently use:
public List<Meter> GetListFromDateRange(DateTime startDateTime, DateTime endDateTime)
{
using (dbContext = new HeatDataVerifEntities())
{
return dbContext.Meters.Where(p => p.Created >= startDateTime && p.Created <= endDateTime).OrderBy(p => p.Created).ToList();
}
}
public int GetCountFromDateRange(DateTime startDateTime, DateTime endDateTime)
{
using (dbContext = new HeatDataVerifEntities())
{
return dbContext.Meters.Where(p => p.Created >= startDateTime && p.Created <= endDateTime).Count();
}
}
Another thing i considered was to create another ActionResult that runs the check for the row size which i would call instead of 'GetListFromDateRange' - and then have that either return an empty partial view along with calling the method for getting the list of item, or returning a partial view that has an error message in it. It just seemed like the should/could be an easier or smarter solution to that.
Again i have been searching around, but as i also mentioned i might simply just be looking at this wrong.
Thanks in advance.

Answer 1

Displaying around 1000 records on one page is not exactly useful, plus it affects many things, such as the performance of your database, depending on how many users request data at the same time, how fast the website displays the data to the users and ultimately your website might crash completely if too many sets of data are requested at the same time.
Instead, why don't you simply add pagination? Decide on a page size, say 20, return those records from your query, together with the number of pages required to display all data. You can then use that to build the page pagination itself. So you never return more than 20 rows from your db, the pressure is minimal, the site runs quickly.
The way you are going now, you are requesting a lot of data, and if you have more than 1000 records all you do is display an error message expecting the user to make another request. You already have the data though, but you're not using it for anything other than a count. Unless a course, all you do is run a count first and then if less than 1000 then you run the actual query.
Model validation is run on inputs, not outputs and I wouldn't suggest you try to change the way MVC works, just to fit a specific scenario which shouldn't happen anyway.
If you want to crack on with your idea then run the count query first, if result is over 1000 then return an error message and display that to the user. You can do this without any kind of custom, non-model validation.

Answer 2

You can always add a custom error message that will show up in ValidationSummary
ModelState.AddModelError(string.Empty, "My own error message");