检查 JObject 中的空或空 JToken [英] Checking for empty or null JToken in a JObject

问题描述

我有以下...

JArray clients = (JArray)clientsParsed["objects"];

foreach (JObject item in clients.Children())
{
    // etc.. SQL params stuff...
    command.Parameters["@MyParameter"].Value = JTokenToSql(item["thisParameter"]);
}

JTokenToSql 看起来像这样...

public static object JTokenToSql(JToken obj)
{
    if (obj.Any())
        return (object)obj;
    else
        return (object)DBNull.Value;
}

我也试过 ((JObject)obj).Count.. 但似乎没有用.

I have tried ((JObject)obj).Count also.. But doesn't seem to be working.

推荐答案

要检查 JObject 上是否存在属性，可以使用方括号语法查看结果是否为 null.如果该属性存在，将始终返回一个 JToken(即使它在 JSON 中具有值 null).

To check whether a property exists on a JObject, you can use the square bracket syntax and see whether the result is null or not. If the property exists, a JToken will be always be returned (even if it has the value null in the JSON).

JToken token = jObject["param"];
if (token != null)
{
    // the "param" property exists
}

如果您手头有一个 JToken 并且您想查看它是否为非空，那么这取决于它是什么类型的 JToken 以及您如何使用定义空".我通常使用这样的扩展方法:

If you have a JToken in hand and you want to see if it is non-empty, well, that depends on what type of JToken it is and how you define "empty". I usually use an extension method like this:

public static class JsonExtensions
{
    public static bool IsNullOrEmpty(this JToken token)
    {
        return (token == null) ||
               (token.Type == JTokenType.Array && !token.HasValues) ||
               (token.Type == JTokenType.Object && !token.HasValues) ||
               (token.Type == JTokenType.String && token.ToString() == String.Empty) ||
               (token.Type == JTokenType.Null);
    }
}

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