How to iterate through Dictionary<string, object> using c#

Question

I have one

Dictionary<string, List<string>> demo = new Dictionary<string, List<string>>();

List<String> key1val= new List<string>();
key1val.Add("1");
key1val.Add("2");
key1val.Add("3");

List<String> key2val= new List<string>();
key2val.Add("4");
key2val.Add("5");

demo.Add("key1", key1val);
demo.Add("key2", key2val);

foreach (var item in demo)
{
    foreach(var it in item.Value)
    {
        Console.WriteLine(it);
    }
}

I want to iterate though all keys like key1,key2 .

if current item is key1 then inside loop should take all values with respect to key1 and iterate it into 2nd loop

loop
iterate though key1
iterate though [1,2,3] 

loop
iterate though key2
iterate though [4,5] 

Answer 1

Well, use 2 nested loops.

The outer one iterating over the keys, the inner one over the values of the corresponding entry :

Dictionary<string, List<string>> demo = new Dictionary<string, List<string>>();

List<String> key1val= new List<string>();
key1val.Add("1");
key1val.Add("2");
key1val.Add("3");

List<String> key2val= new List<string>();
key2val.Add("4");
key2val.Add("5");

demo.Add("key1", key1val);
demo.Add("key2", key2val);

foreach (var key in demo.Keys)
{
    Console.WriteLine(key);
    foreach (var elem in demo[key])
    {
        Console.WriteLine(elem);
    }
}

This outputs

key1
1
2
3
key2
4
5

Answer 2

Using LINQ SelectMany to accumilate values into a single list:

foreach (string value in demo.SelectMany(kvp => kvp.Value))
{
    Console.WriteLine(val);
}

Answer 3

Linq Solution includes Concat to combine Key and Values into a single collection and SelectMany to flatten them:

Dictionary<string, List<string>> demo = ...

var result = demo
  .SelectMany(pair => new string[] { pair.Key }.Concat(pair.Value));  

// Let's have a look
foreach (var item in result)
  Console.WriteLine(item);

Answer 4

foreach (var item in demo )
{
   WriteLine("loop");
   WriteLine($"iterate though {item.key}");
   WriteLine($"iterate though {item.Value}");
   WriteLine();
}

This should output exactly what you want But, you could:

foreach (var item in demo )
{
   WriteLine("loop");
   WriteLine($"iterate though {item.key}");
   if (item.Value is IEnumerable<string> val) foreach(var v in val) WriteLine(v);
   WriteLine();
}

Answer 5

foreach (var item in demo)
{
    Console.WriteLine("loop");
    Console.WriteLine($"iterate though {item.Key}");
    var valueAsString = $"[{String.Join(",", item.Value)}]";
    Console.WriteLine($"iterate though {valueAsString}");
}

Output:

loop
iterate though key1
iterate though [1,2,3]

loop
iterate though key2
iterate though [4,5]

You can test: https://dotnetfiddle.net/REqIdD