Using enum for dropdown list in ASP.NET MVC Core

Question

I\'m trying to create a dropdown list with an enum property in ASP.NET MVC Core using the tag helper in a Razor view:

Here is the model:

public class Per         


        

Answer 1

This is the way to implement Custom TagHelper DropDownList with enum in netcore 3

 


/// 

///  implementation targeting <enum-radio-button> elements with an asp-for attribute, value attribute.
/// 
[HtmlTargetElement("radio-button-enum", Attributes = RadioButtonEnumForAttributeName)]
public class RadioButtonEnumTagHelper : TagHelper
{
    private const string RadioButtonEnumForAttributeName = "asp-for";
    private const string RadioButtonEnumValueAttributeName = "value";

    /// 

    /// Creates a new .
    /// 
    /// The .
    public RadioButtonEnumTagHelper(IHtmlGenerator generator)
    {
        Generator = generator;
    }

    /// 
    public override int Order => -1000;

    [HtmlAttributeNotBound]
    [ViewContext]
    public ViewContext ViewContext { get; set; }

    protected IHtmlGenerator Generator { get; }

    /// 

    /// An expression to be evaluated against the current model.
    /// 
    [HtmlAttributeName(RadioButtonEnumForAttributeName)]
    public ModelExpression For { get; set; }

    [HtmlAttributeName(RadioButtonEnumValueAttributeName)]
    public Enum Value { get; set; }

    /// 
    /// Does nothing if  is null.
    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        if (context == null)
        {
            throw new ArgumentNullException(nameof(context));
        }

        if (output == null)
        {
            throw new ArgumentNullException(nameof(output));
        }

        var childContent = await output.GetChildContentAsync().ConfigureAwait(true);
        string innerContent = childContent.GetContent();
        output.Content.AppendHtml(innerContent);

        output.TagName = "div";
        output.TagMode = TagMode.StartTagAndEndTag;
        output.Attributes.Add("class", "btn-group btn-group-radio");
        
        var modelExplorer = For?.ModelExplorer;
        var metaData = For?.Metadata;

        if (metaData?.EnumNamesAndValues != null)
        {
            foreach (var item in metaData.EnumNamesAndValues)
            {
                string enumId = $"{metaData.ContainerType.Name}_{metaData.PropertyName}_{item.Key}";
                string enumInputLabelName = item.Key.ToString();

                bool enumIsChecked = false;
                if (Value != null)
                {
                    if (enumInputLabelName == Value.ToString())
                    {
                        enumIsChecked = true; }
                }
                else
                {
                    if (For.Model != null && enumInputLabelName == For.Model.ToString())
                    {
                        enumIsChecked = true;
                    }
                }

                var enumResourcedName = metaData.EnumGroupedDisplayNamesAndValues.FirstOrDefault(x => x.Value == item.Value);
                if (enumResourcedName.Value != null)
                {
                    enumInputLabelName = enumResourcedName.Key.Name;
                }

                var enumRadio = Generator.GenerateRadioButton(
                    ViewContext,
                    For.ModelExplorer,
                    metaData.PropertyName,
                    item.Key,
                    false,
                    htmlAttributes: new { @id = enumId });
                enumRadio.Attributes.Remove("checked");
                if (enumIsChecked)
                {
                    enumRadio.MergeAttribute("checked", "checked");
                }
                output.Content.AppendHtml(enumRadio);

                var enumLabel = Generator.GenerateLabel(
                    ViewContext,
                    For.ModelExplorer,
                    For.Name,
                    enumInputLabelName,
                    htmlAttributes: new { @for = enumId, @Class = "btn btn-default" });
                output.Content.AppendHtml(enumLabel);
            }
        }
    }
}