C# – ASP.NET MVC Conditional validation

asp.net-mvccformsvalidation

How to use data annotations to do a conditional validation on model?

For example, lets say we have the following model (Person and Senior):

public class Person
{
    [Required(ErrorMessage = "*")]
    public string Name
    {
        get;
        set;
    }

    public bool IsSenior
    {
        get;
        set;
    }

    public Senior Senior
    {
        get;
        set;
    }
}

public class Senior
{
    [Required(ErrorMessage = "*")]//this should be conditional validation, based on the "IsSenior" value
    public string Description
    {
        get;
        set;
    }
}

And the following view:

<%= Html.EditorFor(m => m.Name)%>
<%= Html.ValidationMessageFor(m => m.Name)%>

<%= Html.CheckBoxFor(m => m.IsSenior)%>
<%= Html.ValidationMessageFor(m => m.IsSenior)%>

<%= Html.CheckBoxFor(m => m.Senior.Description)%>
<%= Html.ValidationMessageFor(m => m.Senior.Description)%>

I would like to be the "Senior.Description" property conditional required field based on the selection of the "IsSenior" propery (true -> required). How to implement conditional validation in ASP.NET MVC 2 with data annotations?

Best Answer

There's a much better way to add conditional validation rules in MVC3; have your model inherit IValidatableObject and implement the Validate method:

public class Person : IValidatableObject
{
    public string Name { get; set; }
    public bool IsSenior { get; set; }
    public Senior Senior { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) 
    { 
        if (IsSenior && string.IsNullOrEmpty(Senior.Description)) 
            yield return new ValidationResult("Description must be supplied.");
    }
}

Related Solutions

Asp.net-mvc – Compile Views in ASP.NET MVC

From the readme word doc for RC1 (not indexed by google)

ASP.NET Compiler Post-Build Step

Currently, errors within a view file are not detected until run time. To let you detect these errors at compile time, ASP.NET MVC projects now include an MvcBuildViews property, which is disabled by default. To enable this property, open the project file and set the MvcBuildViews property to true, as shown in the following example:

<Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <MvcBuildViews>true</MvcBuildViews>
  </PropertyGroup>

Note Enabling this feature adds some overhead to the build time.

You can update projects that were created with previous releases of MVC to include build-time validation of views by performing the following steps:

Open the project file in a text editor.
Add the following element under the top-most <PropertyGroup> element: <MvcBuildViews>true</MvcBuildViews>
At the end of the project file, uncomment the <Target Name="AfterBuild"> element and modify it to match the following:

<Target Name="AfterBuild" Condition="'$(MvcBuildViews)'=='true'">
    <AspNetCompiler VirtualPath="temp" PhysicalPath="$(ProjectDir)\..\$(ProjectName)" />
</Target>

C# – How to create a dropdownlist from an enum in ASP.NET MVC

For MVC v5.1 use Html.EnumDropDownListFor

@Html.EnumDropDownListFor(
    x => x.YourEnumField,
    "Select My Type", 
    new { @class = "form-control" })

For MVC v5 use EnumHelper

@Html.DropDownList("MyType", 
   EnumHelper.GetSelectList(typeof(MyType)) , 
   "Select My Type", 
   new { @class = "form-control" })

For MVC 5 and lower

I rolled Rune's answer into an extension method:

namespace MyApp.Common
{
    public static class MyExtensions{
        public static SelectList ToSelectList<TEnum>(this TEnum enumObj)
            where TEnum : struct, IComparable, IFormattable, IConvertible
        {
            var values = from TEnum e in Enum.GetValues(typeof(TEnum))
                select new { Id = e, Name = e.ToString() };
            return new SelectList(values, "Id", "Name", enumObj);
        }
    }
}

This allows you to write:

ViewData["taskStatus"] = task.Status.ToSelectList();

by using MyApp.Common