下面的代码只在包含唯一值数据时有效:

public string getKey(string Value)
{
    if (dictionary.ContainsValue(Value))
    {
        var ListValueData = new List<string>();
        var ListKeyData   = new List<string>();

        var Values = dictionary.Values;
        var Keys = dictionary.Keys;

        foreach (var item in Values)
        {
            ListValueData.Add(item);
        }

        var ValueIndex = ListValueData.IndexOf(Value);
        foreach (var item in Keys)
        {
            ListKeyData.Add(item);
        }

        return  ListKeyData[ValueIndex];
    }
    return string.Empty;
}

public static string GetKeyFromValue(string valueVar)
{
    foreach (string keyVar in dictionaryVar.Keys)
    {
        if (dictionaryVar[keyVar] == valueVar)
        {
            return keyVar;
        }
    }
    return null;
}

其他人可能有更有效的答案，但我个人觉得这个更直观，对我来说很管用。

types.Values.ToList().IndexOf("one");

values . tolist()将您的字典值转换为对象列表。 IndexOf("one")搜索你的新列表，寻找"one"，并返回与字典中Key/Value对的索引匹配的Index。

这个方法并不关心字典中的键，它只是返回您正在寻找的值的索引。

请记住，在你的字典中可能有不止一个“1”值。这就是没有“get key”方法的原因。

我有一个很简单的方法。这对我来说很完美。

Dictionary<string, string> types = new Dictionary<string, string>();

types.Add("1", "one");
types.Add("2", "two");
types.Add("3", "three");

Console.WriteLine("Please type a key to show its value: ");
string rLine = Console.ReadLine();

if(types.ContainsKey(rLine))
{
    string value_For_Key = types[rLine];
    Console.WriteLine("Value for " + rLine + " is" + value_For_Key);
}

也许是这样的:

foreach (var keyvaluepair in dict)
{
    if(Object.ReferenceEquals(keyvaluepair.Value, searchedObject))
    {
        //dict.Remove(keyvaluepair.Key);
        break;
    }
}

我创建了一个双重查找类:

/// <summary>
/// dictionary with double key lookup
/// </summary>
/// <typeparam name="T1">primary key</typeparam>
/// <typeparam name="T2">secondary key</typeparam>
/// <typeparam name="TValue">value type</typeparam>
public class cDoubleKeyDictionary<T1, T2, TValue> {
    private struct Key2ValuePair {
        internal T2 key2;
        internal TValue value;
    }
    private Dictionary<T1, Key2ValuePair> d1 = new Dictionary<T1, Key2ValuePair>();
    private Dictionary<T2, T1> d2 = new Dictionary<T2, T1>();

    /// <summary>
    /// add item
    /// not exacly like add, mote like Dictionary[] = overwriting existing values
    /// </summary>
    /// <param name="key1"></param>
    /// <param name="key2"></param>
    public void Add(T1 key1, T2 key2, TValue value) {
        lock (d1) {
            d1[key1] = new Key2ValuePair {
                key2 = key2,
                value = value,
            };
            d2[key2] = key1;
        }
    }

    /// <summary>
    /// get key2 by key1
    /// </summary>
    /// <param name="key1"></param>
    /// <param name="key2"></param>
    /// <returns></returns>
    public bool TryGetValue(T1 key1, out TValue value) {
        if (d1.TryGetValue(key1, out Key2ValuePair kvp)) {
            value = kvp.value;
            return true;
        } else {
            value = default;
            return false;
        }
    }

    /// <summary>
    /// get key1 by key2
    /// </summary>
    /// <param name="key2"></param>
    /// <param name="key1"></param>
    /// <remarks>
    /// 2x O(1) operation
    /// </remarks>
    /// <returns></returns>
    public bool TryGetValue2(T2 key2, out TValue value) {
        if (d2.TryGetValue(key2, out T1 key1)) {
            return TryGetValue(key1, out value);
        } else {
            value = default;
            return false;
        }
    }

    /// <summary>
    /// get key1 by key2
    /// </summary>
    /// <param name="key2"></param>
    /// <param name="key1"></param>
    /// <remarks>
    /// 2x O(1) operation
    /// </remarks>
    /// <returns></returns>
    public bool TryGetKey1(T2 key2, out T1 key1) {
        return d2.TryGetValue(key2, out key1);
    }

    /// <summary>
    /// get key1 by key2
    /// </summary>
    /// <param name="key2"></param>
    /// <param name="key1"></param>
    /// <remarks>
    /// 2x O(1) operation
    /// </remarks>
    /// <returns></returns>
    public bool TryGetKey2(T1 key1, out T2 key2) {
        if (d1.TryGetValue(key1, out Key2ValuePair kvp1)) {
            key2 = kvp1.key2;
            return true;
        } else {
            key2 = default;
            return false;
        }
    }

    /// <summary>
    /// remove item by key 1
    /// </summary>
    /// <param name="key1"></param>
    public void Remove(T1 key1) {
        lock (d1) {
            if (d1.TryGetValue(key1, out Key2ValuePair kvp)) {
                d1.Remove(key1);
                d2.Remove(kvp.key2);
            }
        }
    }

    /// <summary>
    /// remove item by key 2
    /// </summary>
    /// <param name="key2"></param>
    public void Remove2(T2 key2) {
        lock (d1) {
            if (d2.TryGetValue(key2, out T1 key1)) {
                d1.Remove(key1);
                d2.Remove(key2);
            }
        }
    }

    /// <summary>
    /// clear all items
    /// </summary>
    public void Clear() {
        lock (d1) {
            d1.Clear();
            d2.Clear();
        }
    }

    /// <summary>
    /// enumerator on key1, so we can replace Dictionary by cDoubleKeyDictionary
    /// </summary>
    /// <param name="key1"></param>
    /// <returns></returns>
    public TValue this[T1 key1] {
        get => d1[key1].value;
    }

    /// <summary>
    /// enumerator on key1, so we can replace Dictionary by cDoubleKeyDictionary
    /// </summary>
    /// <param name="key1"></param>
    /// <returns></returns>
    public TValue this[T1 key1, T2 key2] {
        set {
            lock (d1) {
                d1[key1] = new Key2ValuePair {
                    key2 = key2,
                    value = value,
                };
                d2[key2] = key1;
            }
        }
    }