/// <summary>
/// Returns a valid HTML 4.01 "id" attribute value for an element with the given <paramref name="fullName"/>.
/// </summary>
/// <param name="viewContext">A <see cref="ViewContext"/> instance for the current scope.</param>
/// <param name="fullName">
/// The fully-qualified expression name, ignoring the current model. Also the original HTML element name.
/// </param>
/// <param name="invalidCharReplacement">
/// The <see cref="string"/> (normally a single <see cref="char"/>) to substitute for invalid characters in
/// <paramref name="fullName"/>.
/// </param>
/// <returns>
/// Valid HTML 4.01 "id" attribute value for an element with the given <paramref name="fullName"/>.
/// </returns>
/// <remarks>
/// Similar to <see cref="TagBuilder.CreateSanitizedId"/> but caches value for repeated invocations.
/// </remarks>
public static string CreateSanitizedId(ViewContext viewContext, string fullName, string invalidCharReplacement)
{
if (viewContext == null)
{
throw new ArgumentNullException(nameof(viewContext));
}
if (invalidCharReplacement == null)
{
throw new ArgumentNullException(nameof(invalidCharReplacement));
}
if (string.IsNullOrEmpty(fullName))
{
return(string.Empty);
}
// Check cache to avoid whatever TagBuilder.CreateSanitizedId() may do.
var items = viewContext.HttpContext.Items;
object previousNameAndIdObject;
PreviousNameAndId previousNameAndId = null;
if (items.TryGetValue(PreviousNameAndIdKey, out previousNameAndIdObject) &&
(previousNameAndId = (PreviousNameAndId)previousNameAndIdObject) != null &&
string.Equals(previousNameAndId.FullName, fullName, StringComparison.Ordinal))
{
return(previousNameAndId.SanitizedId);
}
var sanitizedId = TagBuilder.CreateSanitizedId(fullName, invalidCharReplacement);
if (previousNameAndId == null)
{
// Do not create a PreviousNameAndId when TagBuilder.CreateSanitizedId() only examined fullName.
if (string.Equals(fullName, sanitizedId, StringComparison.Ordinal))
{
return(sanitizedId);
}
previousNameAndId = new PreviousNameAndId();
items[PreviousNameAndIdKey] = previousNameAndId;
}
previousNameAndId.FullName = fullName;
previousNameAndId.SanitizedId = sanitizedId;
return(previousNameAndId.SanitizedId);
}
/// <summary>
/// Returns the full HTML element name for the specified <paramref name="expression"/>.
/// </summary>
/// <param name="viewContext">A <see cref="ViewContext"/> instance for the current scope.</param>
/// <param name="expression">Expression name, relative to the current model.</param>
/// <returns>Fully-qualified expression name for <paramref name="expression"/>.</returns>
/// <remarks>
/// Similar to <see cref="TemplateInfo.GetFullHtmlFieldName"/> but caches value for repeated invocations.
/// </remarks>
public static string GetFullHtmlFieldName(ViewContext viewContext, string expression)
{
var htmlFieldPrefix = viewContext.ViewData.TemplateInfo.HtmlFieldPrefix;
if (string.IsNullOrEmpty(expression))
{
return(htmlFieldPrefix);
}
if (string.IsNullOrEmpty(htmlFieldPrefix))
{
return(expression);
}
// Need to concatenate. See if we've already done that.
IDictionary <object, object?> items = viewContext.HttpContext.Items;
PreviousNameAndId? previousNameAndId = null;
if (items.TryGetValue(previousNameAndIdKey, out var previousNameAndIdObject) &&
(previousNameAndId = (PreviousNameAndId?)previousNameAndIdObject) != null &&
string.Equals(previousNameAndId.HtmlFieldPrefix, htmlFieldPrefix, StringComparison.Ordinal) &&
string.Equals(previousNameAndId.Expression, expression, StringComparison.Ordinal))
{
return(previousNameAndId.OutputFullName);
}
if (previousNameAndId is null)
{
previousNameAndId = new PreviousNameAndId();
items[previousNameAndIdKey] = previousNameAndId;
}
previousNameAndId.HtmlFieldPrefix = htmlFieldPrefix;
previousNameAndId.Expression = expression;
if (expression.StartsWith("[", StringComparison.Ordinal))
{
// The expression might represent an indexer access, in which case with a 'dot' would be invalid.
previousNameAndId.OutputFullName = htmlFieldPrefix + expression;
}
else
{
previousNameAndId.OutputFullName = htmlFieldPrefix + "." + expression;
}
return(previousNameAndId.OutputFullName);
}
