在调试过程中，我发现在每个页面的底部放置一个表来显示所有ModelState错误是很有用的。

<table class="model-state">
    @foreach (var item in ViewContext.ViewData.ModelState) 
    {
        if (item.Value.Errors.Any())
        { 
        <tr>
            <td><b>@item.Key</b></td>
            <td>@((item.Value == null || item.Value.Value == null) ? "<null>" : item.Value.Value.RawValue)</td>
            <td>@(string.Join("; ", item.Value.Errors.Select(x => x.ErrorMessage)))</td>
        </tr>
        }
    }
</table>

<style>
    table.model-state
    {
        border-color: #600;
        border-width: 0 0 1px 1px;
        border-style: solid;
        border-collapse: collapse;
        font-size: .8em;
        font-family: arial;
    }

    table.model-state td
    {
        border-color: #600;
        border-width: 1px 1px 0 0;
        border-style: solid;
        margin: 0;
        padding: .25em .75em;
        background-color: #FFC;
    }
 </style>

foreach (ModelState modelState in ViewData.ModelState.Values) {
    foreach (ModelError error in modelState.Errors) {
        DoSomethingWith(error);
    }
}

请参见如何在ASP中获取模型状态错误的集合。净MVC ?。

这是对@Dunc的回答的扩展。参见xml文档注释

// ReSharper disable CheckNamespace
using System.Linq;
using System.Web.Mvc;


public static class Debugg
{
    /// <summary>
    /// This class is for debugging ModelState errors either in the quick watch 
    /// window or the immediate window.
    /// When the model state contains dozens and dozens of properties, 
    /// it is impossible to inspect why a model state is invalid.
    /// This method will pull up the errors
    /// </summary>
    /// <param name="modelState">modelState</param>
    /// <returns></returns>
    public static ModelError[]  It(ModelStateDictionary modelState)
    {
        var errors = modelState.Values.SelectMany(x => x.Errors).ToArray();
        return errors;            
    }
}

此外，ModelState.Values.ErrorMessage可能为空，但ModelState.Values.Exception.Message可能指示一个错误。

基于LINQ版本，如果你想将所有错误消息连接到一个字符串中:

string messages = string.Join("; ", ModelState.Values
                                        .SelectMany(x => x.Errors)
                                        .Select(x => x.ErrorMessage));

var x = new Dictionary<string,string>();
for (var b = 0; b < ViewData.ModelState.Values.Count(); b++)
{
    if (ViewData.ModelState.Values.ElementAt(b).Errors.Count() > 0)
        x.Add(ViewData.ModelState.Keys.ElementAt(b), String.Join(",", ViewData
            .ModelState.Values.ElementAt(b).Errors.Select(c => c.ErrorMessage)));
}