Dictionary<int,string> dict = new Dictionary<int,string>{
  {1,"item1"},
  {2,"item2"},
  {3,"item3"},
}

int key = 2 // for example
string result = dict.ContainsKey(key) ? dict[key] : null;

static void XML_Array(Dictionary<string, string> Data_Array)
{
    String value;
    if(Data_Array.TryGetValue("XML_File", out value))
    {
        // ... Do something here with value ...
    }
}

只需使用字典上的键名。c#有这样的功能:

 Dictionary<string, string> dict = new Dictionary<string, string>();
 dict.Add("UserID", "test");
 string userIDFromDictionaryByKey = dict["UserID"];

如果你看一下建议:

if (Data_Array["XML_File"] != "") String xmlfile = Data_Array["XML_File"];

其实很简单:

String xmlfile = Data_Array["XML_File"];

注意，如果字典没有等于“XML_File”的键，代码将抛出异常。如果你想先检查，你可以像这样使用TryGetValue:

string xmlfile;
if (!Data_Array.TryGetValue("XML_File", out xmlfile)) {
   // the key isn't in the dictionary.
   return; // or whatever you want to do
}
// xmlfile is now equal to the value

private void button2_Click(object sender, EventArgs e)
{
    Dictionary<string, string> Data_Array = new Dictionary<string, string>();
    Data_Array.Add("XML_File", "Settings.xml");

    XML_Array(Data_Array);
}

static void XML_Array(Dictionary<string, string> Data_Array)
{
    String xmlfile = Data_Array["XML_File"];
}