How to find a key in a Dictionary with C#

Mahesh Chand
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Article

Find a Key

The ContainsKey method checks if a key already exists in the dictionary. The following code snippet checks if a key already exits and if not, adds it.

if (!AuthorList.ContainsKey("Mahesh Chand"))
{
AuthorList["Mahesh Chand"] = 20;
}

Find a Value

The ContainsValue method checks if a value already exists in the dictionary. The following code snippet checks if a value already exits.

if (!AuthorList.ContainsValue(9))
{
Console.WriteLine("Item found");
}

Sample

Here is the complete sample code showing how to use these methods.

// Create a dictionary with string key and Int16 value pair
Dictionary<string, Int16> AuthorList = new Dictionary<string, Int16>();
AuthorList.Add("Mahesh Chand", 35);
AuthorList.Add("Mike Gold", 25);
AuthorList.Add("Praveen Kumar", 29);
AuthorList.Add("Raj Beniwal", 21);
AuthorList.Add("Dinesh Beniwal", 84);
// Count
Console.WriteLine("Count: {0}", AuthorList.Count);
// Set Item value
AuthorList["Neel Beniwal"] = 9;
if (!AuthorList.ContainsKey("Mahesh Chand"))
{
AuthorList["Mahesh Chand"] = 20;
}
if (!AuthorList.ContainsValue(9))
{
Console.WriteLine("Item found");
}
// Read all items
Console.WriteLine("Authors all items:");
foreach (KeyValuePair<string, Int16> author in AuthorList)
{
Console.WriteLine("Key: {0}, Value: {1}",
author.Key, author.Value);
}