Mvc: IClientModelValidator MergeAttribute() method

[stap123]

Hi, in the docs here (https://docs.asp.net/en/latest/mvc/models/validation.html#id9) an example of implementing IClientModelValidator is given and in that example a method called MergeAttribute() is called. I have looked through the docs and searched around as best I can but I can't find a reference to this method anywhere.

Which assembly/package is it located in?

Many thanks, keep up the good work.

[Muchiachio]

It's declared in ValidationAttributeAdapterOfTAttribute type which implements IClientModelValidator.
You don't really have to use this method, you can simply set it like this

C# public override void AddValidation(ClientModelValidationContext context) { context.Attributes["data-val"] = "true"; context.Attributes["data-val-custom"] = "Error message"; }

[stap123]

Thanks @Muchiachio , I have done as you suggested for the time being but I was just wondering where it was so that I could use it if I wanted to. I tend to copy what Microsoft do in terms of their elements because I know they have spent more time working out the best/fastest way of developing these things.

[dougbu]

The documentation displays snippets of a working sample, not all the pieces you need. While MVC uses a similar method internally, the better place to look is later in ClassicMovieAttribute. Comments on the doc page such as this one also contain the source.

[donkitchen]

I agree with the comments about the documentation being incomplete. It references a method called GetErrorMessage that is nowhere to be found in the sample code.

[waelkdouh]

They have added the GetErrorMessage. Here it is:

private string GetErrorMessage()
{
return $"Classic movies must have a release year earlier than {_year}.";
}