public static IHtmlContent DropDownListWithTagFor <TModel, TResult>(this IHtmlHelper <TModel> htmlHelper, Expression <Func <TModel, TResult> > expression, string optionLabel, dynamic list,
DropDownCutomValues listOptions, string selectedValue, object htmlAttributes)
{
if (htmlHelper == null)
{
throw new ArgumentNullException(nameof(htmlHelper));
}
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
var expressionProvider = htmlHelper.ViewContext.HttpContext.RequestServices
.GetService(typeof(ModelExpressionProvider)) as ModelExpressionProvider;
var modelExpression = expressionProvider.CreateModelExpression(htmlHelper.ViewData, expression);
string id = modelExpression.Name;
return(DropDownDataTag(htmlHelper, id, modelExpression.ModelExplorer, optionLabel, list, listOptions, selectedValue, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes)));
}
private static IHtmlContent DropDownDataTag(this IHtmlHelper htmlHelper, string id, ModelExplorer modelExplorer, string optionLabel, dynamic list,
DropDownCutomValues listOptions, string selectedValue, object htmlAttributes)
{
string fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(id);
if (String.IsNullOrEmpty(fullName))
{
throw new ArgumentException("id");
}
string htmlOutput = "";
TagBuilder dropdown = new TagBuilder("select");
dropdown.Attributes.Add("name", id);
dropdown.Attributes.Add("id", id);
dropdown.MergeAttributes(HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
StringBuilder options = new StringBuilder();
// Make optionLabel the first item that gets rendered.
if (optionLabel != null)
{
options.Append("<option value='" + String.Empty + "'>" + optionLabel + "</option>");
}
foreach (var item in list)
{
string dataAttributes = string.Empty;
string selectedOption = string.Empty;
if (!string.IsNullOrEmpty(listOptions.DataAttributes))
{
var dataAttributeSplit = listOptions.DataAttributes.Split(',');
if (dataAttributeSplit.Length > 0)
{
foreach (var dataAttribute in dataAttributeSplit)
{
dataAttributes += string.Format("data-{0}='{1}' ", dataAttribute.ToLower().Trim(), DynamicHelper.GetProperty(item, dataAttribute.Trim()));
}
}
}
if (!string.IsNullOrEmpty(selectedValue))
{
if (DynamicHelper.GetProperty(item, listOptions.Value) == selectedValue)
{
selectedOption = "selected='selected'";
}
}
options.Append("<option value='" + DynamicHelper.GetProperty(item, listOptions.Value) + "' " + dataAttributes + " " + selectedOption + ">" + DynamicHelper.GetProperty(item, listOptions.Text) + "</option>");
}
dropdown.InnerHtml.AppendHtml(options.ToString());
if (htmlHelper.ViewData.ModelState.TryGetValue(fullName, out var modelState))
{
if (modelState.Errors.Count > 0)
{
dropdown.AddCssClass(HtmlHelper.ValidationInputCssClassName);
}
}
var validator = htmlHelper.ViewContext.HttpContext.RequestServices.GetService(typeof(ValidationHtmlAttributeProvider)) as ValidationHtmlAttributeProvider;
validator.AddAndTrackValidationAttributes(htmlHelper.ViewContext, modelExplorer, id, dropdown.Attributes);
using (var writer = new StringWriter())
{
dropdown.WriteTo(writer, System.Text.Encodings.Web.HtmlEncoder.Default);
htmlOutput = writer.ToString();
}
return(new HtmlString(htmlOutput));
}