Question

在下面的代码中，我有对象Player的实例，其中包含name，numofmentions，s和salience作为其字段。在第二个for循环中，我为每个玩家对象设置val.s的值。然后我将它们加在一起形成一个总和，这很好。但是在下一个（第三个）for循环中，我想使用每个对象的val.s值，但它返回全零。有人可以告诉我为什么吗？我提前感谢您的帮助

for (int i=0;i<players.Count;i++) 
{
    myList.Add(new Player {name = players[i], numMention=playersNumMentions[i]});
}

var mySummedList = myList.GroupBy(x => x.name).Select(x => new Player { name = x.Key, numMention = x.Sum(y => y.numMention)});

foreach (var val in mySummedList)
{
    if (val.numMention > 50000) //differs for different problems
    {
        sql = "SELECT COUNT(Actor1Code) AS S FROM [gdelt-bq:full.events] WHERE Year>=" + predictionDate + " AND (Actor1Code ='" + val.name + "' AND ((Actor2CountryCode = '" + mainPlayer1 + "') OR (Actor2CountryCode='" + mainPlayer2 + "')))";
        response = new WebClient().DownloadString(url + "?q=" + Uri.EscapeUriString(sql));
        value = JsonValue.Parse(response);

        result = value as JsonObject;
        var row = result["modelData"]["rows"][0];
        val.s=((int)row["f"][0]["v"]);

        sumOfS += val.s;                
    }         
}

foreach (var val in mySummedList)
{
    if (val.numMention > 50000) //differs for different problems
    {                             
        val.salience = val.s / sumOfS;

        Console.WriteLine(String.Format("{0}: {1}", val.name, val.salience));
    }
}

Answer 1

您正在使用LINQ的Select，它可以懒惰地评估可枚举：

.Select(x => new Player { name = x.Key, numMention = x.Sum(y => y.numMention)});

如果您需要重用Player实例，请在选择后尝试调用ToList：

var mySummedList = myList.GroupBy(x => x.name).Select(x => new Player { name = x.Key, numMention = x.Sum(y => y.numMention)}).ToList();

Answer 2

我认为这是因为这一行

val.salience = val.s / sumOfS;

因为sumOfS大于val.s并且它是整数除法，所以结果为零。

您可以将val.salience类型更改为double并将行更改为

val.salience = val.s / (double)sumOfS;

Answer 3

如果Player是一个结构，它将无法工作，如果它是一个类改变foreach而不是

foreach(var x.....)

DO

foreach(Player x....)

并确保val.s的值与0

不同

对象字段不保留值

3 个答案: