How to avoid null key errors in dictionary?

How to avoid error if key is null?

//Getter/setter
public static Dictionary<string, string> Dictionary
{
    get { return Global.dictionary; }
    set { Global.dictionary = value; }
}

UPDATE:

Dictionary.Add("Key1", "Text1");
Dictionary["Key2"] <-error! so wh开发者_高级运维at can I write in the GET to avoid error?

Thanks.

regards

Use TryGetValue:

Dictionary<int, string> dict = ...;
string value;

if (dict.TryGetValue(key, out value))
{
    // value found
    return value;
}
else
{
    // value not found, return what you want
}

You can use the Dictionary.ContainsKey method.

So you'd write:

if (myDictionary.ContainsKey("Key2"))
{
    // Do something.
}

The other alternatives are to either wrap the access in a try...catch block or use TryGetValue (see the examples on the MSDN page linked to).

string result = null;
if (dict.TryGetValue("Key2", out result))
{
    // Do something with result
}

The TryGetMethod is more efficient if you want do something with the result as you don't need a second call to get the value (as you would with the ContainsKey method).

(Of course, in both methods you'd replace "Key2" with a variable.)

An extension method:

public static TValue GetValue<TKey, TValue>(this Dictionary<TKey, TValue> dic, TKey key)
{
    TValue result;
    return dic.TryGetValue(key, out result) ?
        result :
        default(TValue);
}

Usage:

var dic = new Dictionary<string, string>
{
   { "key", "value" }
};

string r1 = dic.GetValue("key"); // "value"
string r2 = dic.GetValue("false"); // null

A key can never be null in a dictionary. A dictionary is a hashtable where by definition you need a non-empty key or the hash function cannot map to the corresponding element.

You're returning the wrong thing. Don't return the dictionary, pass in a key and return the value.

public static string GetValue(string key)
{
    if(Global.dictionary.ContainsKey(key))
    {
        return Global.dictionary[key];
    }

    return ""; // or some other value
}