An HTML Helper for creating an array of checkboxes.

HtmlHelpers.cs

public static class HtmlHelpers
{
  public static IHtmlString ArrayCheckBoxFor<TModel, TArray>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TArray[]>> expression, TArray value)
  {
    ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
    
    var tagBuilder = new TagBuilder("input");
    tagBuilder.Attributes.Add("type", "checkbox");
    tagBuilder.Attributes.Add("name", metadata.PropertyName);  
    tagBuilder.Attributes.Add("value", value.ToString());
  
    TArray[] propertyValue = metadata.Model as TArray[];
    bool isContainedInArray = propertyValue != null && propertyValue.Contains(value);
    if (isContainedInArray)
      tagBuilder.Attributes.Add("checked", "checked");
    
    return MvcHtmlString.Create(tagBuilder.ToString(TagRenderMode.SelfClosing));
  }
}

MyModel.cs

public class MyModel
{
  // This must be an array. It can be an array of IDs if the
  // list of possible values is pulled from a database.
  public string[] Flowers { get; set; }
}

output.html

<label>
  <input type="checkbox" name="Flowers" value="Lilacs" checked="checked"/> Lilacs
</label>
<label>
  <input type="checkbox" name="Flowers" value="Marigolds"/> Marigolds
</label>
<label>
  <input type="checkbox" name="Flowers" value="Roses" checked="checked"/> Roses
</label>

template.cshtml

@model MyModel

<label>
  @Html.ArrayCheckBoxFor(x => x.Flowers, "Lilacs") Lilacs
</label>
<label>
  @Html.ArrayCheckBoxFor(x => x.Flowers, "Marigolds") Marigolds
</label>
<label>
  @Html.ArrayCheckBoxFor(x => x.Flowers, "Roses") Roses
</label>