问题

要在API的POST请求中传递一个空值给一个键，你可以像下面这样做。

例如，我想传递以下JSON数据，即Exp和TeamID为null。

{
   "ID": 162617,
   "TextKey": "107737",
   "Exp": null,
   "TeamID": null
}

这个结果在Postman中是被接受的，但是当我尝试在C#代码中使用相同的方式传递时，我的JSON内容变得无效。

long idvalue = 162617;
string textkeyvalue = "107737";
string expvalue = null;
long? teamIDvalue = null;

string postData = "{\"ID\":" + idvalue + ",\"TextKey\":\"" + textkeyvalue + "\",\"Exp\":" + expvalue + ",\"TeamID\":" + teamIDvalue + "}";

这给我以下输出。

{
   "ID": 162617,
   "TextKey": "107737",
   "Exp": "",
   "TeamID":
}

我的请求由于无效的JSON主体而失败。那么，如何传递这种类型的null数据或null关键字呢？

注意：在我的API中，所有键值对都是强制的，所以如果它们为null，我不能省略它们。

我只想以以下格式传递数据。

{
   "ID": 162617,
   "TextKey": "107737",
   "Exp": null,
   "TeamID": null
}

long idvalue = 162617;
string textkeyvalue = "107737";
string expvalue = null;
long? teamIDvalue = null;

string postData = "{\"ID\":" + idvalue + ",\"TextKey\":\"" + textkeyvalue + "\",\"Exp\":\"" + expvalue + "\",\"TeamID\":\"" + teamIDvalue + "\"}";

答案1

得分: 3

以下是翻译好的代码部分：

要回答你的问题，以便为 null 值编写文本，你可以这样做：

var result = "my value is " + (strValue ?? "null");

或者要添加引号：

var result = "my value is " + (strValue == null ? "null" : $"\"{strValue}\"");

你还可以创建静态辅助方法以使其更容易：

static string write(string str) => str == null ? "null" : $"\"{str}\"";
static string write(long? value) => value == null ? "null" : value.ToString();

因此，在你的示例中，它变成了：

string postData = "{"ID":" + idvalue + ","TextKey":" + write(textkeyvalue) +
                  ","Exp":" + write(expvalue) + ","TeamID":" +
                  write(teamIDvalue) + "}";

更好的解决方案！

创建一个用于数据模型的类，并使用库（例如 System.Text.Json）来对其进行序列化，如下所示：

public class MyData
{
   public long ID { get; set; }
   public string TextKey { get; set; }
   public string Exp { get; set; }
   public long? TeamID { get; set; }
}

// 构造模型
var data = new MyData()
{
   ID = 162617,
   TextKey = "107737",
   Exp = null,
   TeamID = null,
}

// 序列化为 JSON
var result = System.Text.Json.JsonSerializer.Serialize(data);

<details>
<summary>英文:</summary>

To answer your question, to write text for a null value, you can do this:

```cs
var result = &quot;my value is &quot; + (strValue ?? &quot;null&quot;);

Or to add quotes:

var result = "my value is " + (strValue == null ? "null" : $"\"{strValue}\"");

You can also create static helper methods to make it easier:

static string write(string str) => str == null ? "null" : $"\"{str}\"";
static string write(long? value) => value == null ? "null" : value.ToString();

So in your example, it becomes:

string postData = "{\"ID\":" + idvalue + ",\"TextKey\":" + write(textkeyvalue) +
                  ",\"Exp\":" + write(expvalue) + ",\"TeamID\":" +
                  write(teamIDvalue) + "}";

<br/>

Better solution!

Create a class for the data model, and use a library (for example, System.Text.Json) to serialize it, like so:

public class MyData
{
   public long ID { get; set; }
   public string TextKey { get; set; }
   public string Exp { get; set; }
   public long? TeamID { get; set; }
}

// Construct model
var data = new MyData()
{
   ID = 162617,
   TextKey = "107737",
   Exp = null,
   TeamID = null,
}

// Serialize to JSON
var result = System.Text.Json.JsonSerializer.Serialize(data);

答案2

得分: 3

gepa's answer 答案非常准确，但你也可以序列化一个匿名对象：

long idvalue = 162617;
string textkeyvalue = "107737";
string? expvalue = null;
long? teamIDvalue = null;

string postData = System.Text.Json.JsonSerializer.Serialize(new
{
    ID = idvalue,
    TextKey = textkeyvalue,
    Exp = expvalue,
    TeamID = teamIDvalue,
});

long idvalue = 162617;
string textkeyvalue = "107737";
string? expvalue = null;
long? teamIDvalue = null;

string postData = System.Text.Json.JsonSerializer.Serialize(new
{
    ID = idvalue,
    TextKey = textkeyvalue,
    Exp = expvalue,
    TeamID = teamIDvalue,
});