C# HtmlHelper.GetModelStateValue方法代码示例

        public static IEnumerable<SelectListItem> GetSelectListItems(HtmlHelper html, ISelectListBuilder dropDownList, string expressionText)
        {
            string fullHtmlFieldName = html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(expressionText);

            bool flag = false;

            IEnumerable<SelectListItem> selectList = dropDownList.SelectList();
            bool allowMultiple = dropDownList.Attr("multiple") == "multiple";

            if (selectList == null)
            {
                selectList = html.GetSelectListItemsFromViewData(expressionText);
                flag = true;
            }
            object defaultValue = allowMultiple ? html.GetModelStateValue(fullHtmlFieldName, typeof(string[])) : html.GetModelStateValue(fullHtmlFieldName, typeof(string));
            if (!flag && defaultValue == null && !String.IsNullOrEmpty(expressionText))
            {
                defaultValue = html.ViewData.Eval(expressionText);
            }
            if (defaultValue != null)
            {
                selectList = GetSelectListWithDefaultValue(selectList, defaultValue, allowMultiple);
            }
            return selectList;
        }

        private static MvcHtmlString SelectInternal(HtmlHelper htmlHelper, string optionLabel, string name, IEnumerable<SelectListItem> selectList, ModelMetadata metadata, bool allowMultiple, IDictionary<string, object> htmlAttributes)
        {
            var fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
            if (string.IsNullOrEmpty(fullName))
                throw new ArgumentNullException("name");

            var usedViewData = false;

            // If we got a null selectList, try to use ViewData to get the list of items.
            if (selectList == null)
            {
                selectList = htmlHelper.GetSelectData(fullName);
                usedViewData = true;
            }

            object defaultValue = (allowMultiple) ? htmlHelper.GetModelStateValue(fullName, typeof(string[])) : htmlHelper.GetModelStateValue(fullName, typeof(string));

            // If we haven't already used ViewData to get the entire list of items then we need to
            // use the ViewData-supplied value before using the parameter-supplied value.
            if (!usedViewData)
            {
                if (defaultValue == null)
                {
                    defaultValue = htmlHelper.ViewData.Eval(fullName);
                }
            }

            if (defaultValue != null)
            {
                var defaultValues = (allowMultiple) ? defaultValue as IEnumerable : new[] { defaultValue };
                var values = from object value in defaultValues select Convert.ToString(value, CultureInfo.CurrentCulture);
                var selectedValues = new HashSet<string>(values, StringComparer.OrdinalIgnoreCase);
                var newSelectList = new List<SelectListItem>();

                foreach (var item in selectList)
                {
                    item.Selected = (item.Value != null) ? selectedValues.Contains(item.Value) : selectedValues.Contains(item.Text);
                    newSelectList.Add(item);
                }
                selectList = newSelectList;
            }

            // Convert each ListItem to an <option> tag
            var listItemBuilder = new StringBuilder();

            // Make optionLabel the first item that gets rendered.
            if (optionLabel != null)
            {
                listItemBuilder.AppendLine(ListItemToOption(new SelectListItem { Text = optionLabel, Value = String.Empty, Selected = false }));
            }

            foreach (var item in selectList)
            {
                listItemBuilder.AppendLine(ListItemToOption(item));
            }

            var tagBuilder = new TagBuilder("select")
            {
                InnerHtml = listItemBuilder.ToString()
            };
            tagBuilder.MergeAttributes(htmlAttributes);
            tagBuilder.MergeAttribute("name", fullName, true /* replaceExisting */);
            tagBuilder.GenerateId(fullName);
            if (allowMultiple)
            {
                tagBuilder.MergeAttribute("multiple", "multiple");
            }

            // If there are any errors for a named field, we add the css attribute.
            ModelState modelState;
            if (htmlHelper.ViewData.ModelState.TryGetValue(fullName, out modelState))
            {
                if (modelState.Errors.Count > 0)
                {
                    tagBuilder.AddCssClass(HtmlHelper.ValidationInputCssClassName);
                }
            }

            tagBuilder.MergeAttributes(htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata));

            return new MvcHtmlString(tagBuilder.ToString(TagRenderMode.Normal));
        }