默认设置为DisplayFormatAttribute.ConvertEmptyStringToNull为假

问题描述

我只是转换了一堆Web服务的Web API2。现在，我的C＃code吹起来的时候，浏览器发送一个空字符串，并进入我的code转换为null。我研究，我已经找到工作，为我的全球解决方案，没有。

I just converted a bunch of web services to Web API2. Now my C# code blows up when the browser sends an empty string and it enters my code converted to null. I have researched global solutions and none that I have found work for me.

我当然可以手动设置为我所有Web API车型每字符串，但我有几十款所以才会preFER一个全球性的解决方案。

I can of course set it manually for every string in all my Web API models, but I have scores of models so would prefer a global solution.

在这里去过：string.empty转换为null时传递JSON对象MVC控制器以及其他页面，并企图实现每个解决方案，但都无济于事。

Been here: string.empty converted to null when passing JSON object to MVC Controller and other pages and attempted to implement each solution, but to no avail.

我怎样才能为全球的ConvertEmptyStringToNull默认设置为false？

How can I globally set the default for ConvertEmptyStringToNull to false?

推荐答案

您需要换出 ModelMetadataProvider 有一个设置 ConvertEmptyStringToNull 到假

You need to swap out the ModelMetadataProvider with one that sets the ConvertEmptyStringToNull to false

如：

public class EmptyStringAllowedModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override CachedDataAnnotationsModelMetadata CreateMetadataFromPrototype(CachedDataAnnotationsModelMetadata prototype, Func<object> modelAccessor)
    {
        var metadata = base.CreateMetadataFromPrototype(prototype, modelAccessor);
        metadata.ConvertEmptyStringToNull = false;
        return metadata;
    }

    protected override CachedDataAnnotationsModelMetadata CreateMetadataPrototype(IEnumerable<Attribute> attributes, Type containerType, Type modelType, string propertyName)
    {
        var metadata = base.CreateMetadataPrototype(attributes, containerType, modelType, propertyName);
        metadata.ConvertEmptyStringToNull = false;
        return metadata;
    }
}

您会在你的WebApiConfig像注册：

You would register in your WebApiConfig like:

config.Services.Replace（typeof运算（ModelMetadataProvider），新EmptyStringAllowedModelMetadataProvider（））;

这是由 https://gist.github.com/nakamura-to/4029706

This was inspired by https://gist.github.com/nakamura-to/4029706

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