如何设置文本框空字符串的默认值而不是空值

I may be out of date, but one principle I adhere to is avoid nulls as much as possible.

我可能已经过时了，但我坚持的一个原则是尽量避免无效。

However what I have found is that for a strongly typed view in which the user inputs the properties of an object I want to save, if some fields are not entered they are assigned as null.

然而，我发现，对于一个强类型视图，用户输入我想要保存的对象的属性，如果没有输入某些字段，它们将被赋值为null。

Then when you try to save the changes, the validation fails.

然后，当您尝试保存更改时，验证失败。

So rather than set each property to an empty string, how can I automatically set each TextBox on a form to default to an empty string rather than a null?

因此，与其将每个属性设置为空字符串，如何将表单中的每个文本框自动设置为空字符串而不是null?

4 个解决方案

#1

You could put the following attribute on your string-properties in your model:

您可以将以下属性放在模型中的字符串属性:

[DisplayFormat(ConvertEmptyStringToNull=false)]

So whenever someone posts a form with empty text-fields, these will be an empty string instead of null...

因此，每当有人用空文本字段发布一个表单时，这些都将是空字符串，而不是空字符串。

#2

To be honest, I'd say your coding methodology is out of date and flawed. You should handle all possibilities, it's not hard. That's exactly what string.IsNullOrEmpty(value); is for.

老实说，我觉得你的编码方法过时了，而且有缺陷。你应该处理所有的可能性，这并不难。这正是string.IsNullOrEmpty(价值);是对的。

I'm guessing your validation logic is something like:

我猜你的验证逻辑是这样的:

if (value == string.Empty) { isValid = false; }

So it doesn't handle the null values. You should replace that check so it also checks for nulls.

它不处理空值。您应该替换那个检查，以便它也检查null。

string value1 = null;
string value2 = string.Empty;

string.IsNullOrEmpty(value1); // true
string.IsNullOrEmpty(value2); // true

#3

An alternative solution to using attributes on each model property, as described in the accepted answer, is using a custom model binder, see string.empty converted to null when passing JSON object to MVC Controller

在每个模型属性上使用属性的另一种解决方案，如被接受的答案中所描述的，是使用自定义模型绑定器，参见字符串。将JSON对象传递给MVC控制器时，将其转换为null

#4

I ran across this problem when dealing with an old service that requires empty strings. I created an extension method:

我在处理需要空字符串的旧服务时遇到了这个问题。我创建了一个扩展方法:

public static string GetValueOrDefault(this string str)
        {
            return str ?? String.Empty;
        }

So you can use this when you want to make sure any strings that are null become empty

所以你可以用这个来确保任何空的字符串都是空的

yourString1.GetValueOrDefault();
yourString2.GetValueOrDefault();

#1