c# - 参数异常 "Item with Same Key has already been added"

Question

我不断收到以下代码的错误:

Dictionary<string, string> rct3Features = new Dictionary<string, string>();
Dictionary<string, string> rct4Features = new Dictionary<string, string>();

foreach (string line in rct3Lines) 
{
    string[] items = line.Split(new String[] { " " }, 2, StringSplitOptions.None);

    rct3Features.Add(items[0], items[1]);

    ////To print out the dictionary (to see if it works)
    //foreach (KeyValuePair<string, string> item in rct3Features)
    //{
    //    Console.WriteLine(item.Key + " " + item.Value);
    //}

}

错误抛出一个 ArgumentException 说，

"An item with the same key has already been added."

经过多次 Google 搜索后，我不确定如何解决此问题。

在代码的后面，我需要访问字典以实现比较功能:

Compare4To3(rct4Features, rct3Features);

public static void Compare4To3(Dictionary<string, string> dictionaryOne, Dictionary<string, string> dictionaryTwo)
{
    //foreach (string item in dictionaryOne)
    //{

    //To print out the dictionary (to see if it works)
    foreach (KeyValuePair<string, string> item in dictionaryOne)
    {
        Console.WriteLine(item.Key + " " + item.Value);
    }

        //if (dictionaryTwo.ContainsKey(dictionaryOne.Keys)
        //{
        //    Console.Write("True");
        //}
        //else
        //{
        //    Console.Write("False");
        //}
    //}
}

此功能未完成，但我正在尝试解决此异常。我可以通过哪些方法修复此异常错误，并继续访问用于此功能的字典？谢谢

Answer 1

这个错误是不言自明的。字典键是唯一的，您不能拥有多个相同的键。要解决此问题，您应该像这样修改代码:

Dictionary<string, string> rct3Features = new Dictionary<string, string>();
Dictionary<string, string> rct4Features = new Dictionary<string, string>();

foreach (string line in rct3Lines) 
{
    string[] items = line.Split(new String[] { " " }, 2, StringSplitOptions.None);

    if (!rct3Features.ContainsKey(items[0]))
    {
        rct3Features.Add(items[0], items[1]);
    }

    ////To print out the dictionary (to see if it works)
    //foreach (KeyValuePair<string, string> item in rct3Features)
    //{
    //    Console.WriteLine(item.Key + " " + item.Value);
    //}
}

这个简单的 if 语句确保您仅在键 (items[0]) 不存在时才尝试向字典添加新条目。