Show “NULL” for null values in ASP.NET MVC DisplayFor Html Helper

问题

Is there a way to get an @Html.DisplayFor value to show "NULL" in the view if the value of the model item is null?

Here's an example of an item in my Details view that I'm working on currently. Right now if displays nothing if the value of the Description is null.

<div class="display-field">
    @Html.DisplayFor(model => model.Description)
</div>

回答1:

yes, I would recommend using the following data annotation with a nullable datetime field in your codefirst model :

[Display(Name = "Last connection")]
[DisplayFormat(NullDisplayText = "Never connected")]
public DateTime? last_connection { get; set; }

then in your view :

@Html.DisplayFor(x => x.last_connection)

回答2:

Display a string e.g. "-" in place of null values show via the "DisplayFor" standard helper using a helper extension, i.e. "DisplayForNull"

1. Create Folder "Helpers" and add a new controller "Helper.cs"

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Linq.Expressions;
using System.Web;
using System.Web.Mvc;

namespace WIPRO.Helpers
{
    public static class Helpers
    {
        public static MvcHtmlString DisplayForNull<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression)
        {
            var metaData = ModelMetadata.FromLambdaExpression(expression, helper.ViewData);

        string valuetodisplay = string.Empty;

        if (metaData.Model != null)
        {
            if (metaData.DisplayFormatString != null)
            {
                valuetodisplay = string.Format(metaData.DisplayFormatString, metaData.Model);

            }
            else
            {
                valuetodisplay = metaData.Model.ToString();

            }

        }
        else
        {
            valuetodisplay = "-";

        }

        return MvcHtmlString.Create(valuetodisplay);

    }

}

2. In your view

@using WIPRO.Helpers

@Html.DisplayForNull(model => model.CompanyOwnerPersonName)

in place of

@Html.DisplayFor(model => model.CompanyOwnerPersonName)

Hope it helps ;-)

来源：https://stackoverflow.com/questions/15981594/show-null-for-null-values-in-asp-net-mvc-displayfor-html-helper

标签

asp.net-mvc

razor

html-helper