我正在与c#MVC2和ASP合作.网我的一个表单包含一个文件输入字段，允许用户 Select 任何文件类型，然后将其转换为blob并保存到数据库中.我的问题是，每当用户 Select 的文件超过一定数量的Mb(约8)时，就会出现如下页面错误:
The connection was reset
The connection to the server was reset while the page was loading.
我不介意用户上传的文件有8Mb的限制，但是我需要阻止当前错误的发生，并显示正确的验证消息(最好使用ModelState.AddModelError函数).有人能帮我吗？我似乎无法在页面中发生任何其他事情之前"捕获"错误，因为它发生在控制器内的上载函数中之前.
一种可能性是编写自定义验证属性:
public class MaxFileSizeAttribute : ValidationAttribute
{
private readonly int _maxFileSize;
public MaxFileSizeAttribute(int maxFileSize)
{
_maxFileSize = maxFileSize;
}
public override bool IsValid(object value)
{
var file = value as HttpPostedFileBase;
if (file == null)
{
return false;
}
return file.ContentLength <= _maxFileSize;
}
public override string FormatErrorMessage(string name)
{
return base.FormatErrorMessage(_maxFileSize.ToString());
}
}
然后您可以拥有一个视图模型:
public class MyViewModel
{
[Required]
[MaxFileSize(8 * 1024 * 1024, ErrorMessage = "Maximum allowed file size is {0} bytes")]
public HttpPostedFileBase File { get; set; }
}
控制器:
public class HomeController : Controller
{
public ActionResult Index()
{
return View(new MyViewModel());
}
[HttpPost]
public ActionResult Index(MyViewModel model)
{
if (!ModelState.IsValid)
{
// validation failed => redisplay the view
return View(model);
}
// the model is valid => we could process the file here
var fileName = Path.GetFileName(model.File.FileName);
var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
model.File.SaveAs(path);
return RedirectToAction("Success");
}
}
还有一个观点:
@model MyViewModel
@using (Html.BeginForm(null, null, FormMethod.Post, new { enctype = "multipart/form-data" }))
{
@Html.TextBoxFor(x => x.File, new { type = "file" })
@Html.ValidationMessageFor(x => x.File)
<button type="submit">OK</button>
}
现在，当然，为了让这项功能发挥作用，你必须增加允许的最大上传文件大小.配置为足够大的值:
<!-- 1GB (the value is in KB) -->
<httpRuntime maxRequestLength="1048576" />
对于IIS7:
<system.webServer>
<security>
<requestFiltering>
<!-- 1GB (the value is in Bytes) -->
<requestLimits maxAllowedContentLength="1073741824" />
</requestFiltering>
</security>
</system.webServer>
现在，我们可以进一步使用自定义验证属性，并启用客户端验证以避免浪费带宽.当然，上传前验证文件大小只能使用HTML5 File API.因此，只有支持该API的浏览器才能利用它.
因此，第一步是让我们的自定义验证属性实现IClientValidatable接口，这将允许我们在javascript中附加一个自定义适配器:
public class MaxFileSizeAttribute : ValidationAttribute, IClientValidatable
{
private readonly int _maxFileSize;
public MaxFileSizeAttribute(int maxFileSize)
{
_maxFileSize = maxFileSize;
}
public override bool IsValid(object value)
{
var file = value as HttpPostedFileBase;
if (file == null)
{
return false;
}
return file.ContentLength <= _maxFileSize;
}
public override string FormatErrorMessage(string name)
{
return base.FormatErrorMessage(_maxFileSize.ToString());
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
var rule = new ModelClientValidationRule
{
ErrorMessage = FormatErrorMessage(_maxFileSize.ToString()),
ValidationType = "filesize"
};
rule.ValidationParameters["maxsize"] = _maxFileSize;
yield return rule;
}
}
剩下的就是配置自定义适配器了:
jQuery.validator.unobtrusive.adapters.add(
'filesize', [ 'maxsize' ], function (options) {
options.rules['filesize'] = options.params;
if (options.message) {
options.messages['filesize'] = options.message;
}
}
);
jQuery.validator.addMethod('filesize', function (value, element, params) {
if (element.files.length < 1) {
// No files selected
return true;
}
if (!element.files || !element.files[0].size) {
// This browser doesn't support the HTML5 API
return true;
}
return element.files[0].size < params.maxsize;
}, '');