Make HTML helper parameter names consistent

[dougbu]

The current MVC 6.0 parameter names are inconsistent between the HTML helper methods. This is a chance to clean up those inconsistencies. Fortunately I can only find a few shared parameters with multiple names. Unfortunately changing the first example below would introduce a small breaking change between MVC 5.2 and 6.0, affecting people using named parameters when calling these methods. (The parameter names look like they were carried over from MVC 5.2 but I didn't check carefully.)

For the string expression name parameters in IHtmlHelper:

• @Html.CheckBox() and most others use the parameter "name"
• @Html.DisplayName() and some others use the parameter "expression"
• @Html.ValidationMessage() uses the parameter "modelName"

With the possible exception of @Html.Display() and @Html.Editor(), should name this parameter "name" everywhere. Making an exception for those two because they have multiple name-related parameters.

The other option would be to use "shortName" everywhere but for @Html.GenerateIdFromName(). That exception is the only one that takes a fully-qualified expression name. Everything else takes an expression name relative to the current model.

For the IHtmlHelper or IHtmlHelper<TModel> parameters of the extension methods:

• @Html.CheckBox() and most others use the parameter "htmlHelper"
• @Html.Display() and some others use the parameter "html"
• @Html.ActionLink() uses the parameter "helper"

"htmlHelper" seems fine to use everywhere.

For the expression result type parameter:

• @Html.HiddenFor() and most others use the type parameter name "TProperty"
• @Html.DisplayFor() and a few less others use the type parameter name "TValue"

Though less-used, "TValue" is actually more correct. "TResult" might be better still.

[dougbu]

decided on the following:

• name all string expression name and Expression<Func<TModel, TResult>> parameters "expression"
  • single special case is GenerateIdFromName(string fullName) since every other expression name is relative to the current ViewData,TemplateInfo.HtmlFieldPrefix value
• name all this parameters of type IHtmlHelper or IHtmlHelper<TModel> "htmlHelper"
• rename TProperty and TValue to TResult

[dougbu]

Fixed in commits 8eb6327 and 966bfeb

[dougbu]

Removed Task label so this minor breaking change shows up in the next release notes. Unlikely anyone is using named parameters here but just in case...