/// <summary>
/// Gets <see cref="ViewDataInfo"/> for named <paramref name="expression"/> in given
/// <paramref name="viewData"/>.
/// </summary>
/// <param name="viewData">
/// The <see cref="ViewDataDictionary"/> that may contain the <paramref name="expression"/> value.
/// </param>
/// <param name="expression">Expression name, relative to <c>viewData.Model</c>.</param>
/// <returns>
/// <see cref="ViewDataInfo"/> for named <paramref name="expression"/> in given <paramref name="viewData"/>.
/// </returns>
public static ViewDataInfo Eval([NotNull] ViewDataDictionary viewData, string expression)
{
// While it is not valid to generate a field for the top-level model itself because the result is an
// unnamed input element, do not throw here if full name is null or empty. Support is needed for cases
// such as Html.Label() and Html.Value(), where the user's code is not creating a name attribute. Checks
// are in place at higher levels for the invalid cases.
var fullName = viewData.TemplateInfo.GetFullHtmlFieldName(expression);
// Given an expression "one.two.three.four" we look up the following (pseudo-code):
// this["one.two.three.four"]
// this["one.two.three"]["four"]
// this["one.two"]["three.four]
// this["one.two"]["three"]["four"]
// this["one"]["two.three.four"]
// this["one"]["two.three"]["four"]
// this["one"]["two"]["three.four"]
// this["one"]["two"]["three"]["four"]
// Try to find a matching ViewData entry using the full expression name. If that fails, fall back to
// ViewData.Model using the expression's relative name.
var result = EvalComplexExpression(viewData, fullName);
if (result == null)
{
if (string.IsNullOrEmpty(expression))
{
// Null or empty expression name means current model even if that model is null.
result = new ViewDataInfo(container: viewData, value: viewData.Model);
}
else
{
result = EvalComplexExpression(viewData.Model, expression);
}
}
return(result);
}
/// <summary>
/// Gets <see cref="ViewDataInfo"/> for named <paramref name="expression"/> in given
/// <paramref name="viewData"/>.
/// </summary>
/// <param name="viewData">
/// The <see cref="ViewDataDictionary"/> that may contain the <paramref name="expression"/> value.
/// </param>
/// <param name="expression">Expression name, relative to <c>viewData.Model</c>.</param>
/// <returns>
/// <see cref="ViewDataInfo"/> for named <paramref name="expression"/> in given <paramref name="viewData"/>.
/// </returns>
public static ViewDataInfo Eval([NotNull] ViewDataDictionary viewData, string expression)
{
// While it is not valid to generate a field for the top-level model itself because the result is an
// unnamed input element, do not throw here if full name is null or empty. Support is needed for cases
// such as Html.Label() and Html.Value(), where the user's code is not creating a name attribute. Checks
// are in place at higher levels for the invalid cases.
var fullName = viewData.TemplateInfo.GetFullHtmlFieldName(expression);
// Given an expression "one.two.three.four" we look up the following (pseudo-code):
// this["one.two.three.four"]
// this["one.two.three"]["four"]
// this["one.two"]["three.four]
// this["one.two"]["three"]["four"]
// this["one"]["two.three.four"]
// this["one"]["two.three"]["four"]
// this["one"]["two"]["three.four"]
// this["one"]["two"]["three"]["four"]
// Try to find a matching ViewData entry using the full expression name. If that fails, fall back to
// ViewData.Model using the expression's relative name.
var result = EvalComplexExpression(viewData, fullName);
if (result == null)
{
if (string.IsNullOrEmpty(expression))
{
// Null or empty expression name means current model even if that model is null.
result = new ViewDataInfo(container: viewData, value: viewData.Model);
}
else
{
result = EvalComplexExpression(viewData.Model, expression);
}
}
return result;
}