C# dictionary initialization

Is here any ways to initialize dictionary key-value pair with same values without copying code?
For example like this:

Dictionary<string, IReadonlyCollection<string>> dic = new() 
{
    ["someKey"] = new[] { <value from key "someKey">, "anotherValue", ect... }
}

Update:

Dictionary<string,string[]> _dict = new(GetPairs());

KeyValuePair<string, string[]>[] GetPairs()
{ 
 GetPair("key", "value", "value2"),
}

KeyValuePair<string, string[]> GetPair(string key, params string[] values) 
{
    var values2 = new[] { key }; 

    return new KeyValuePair<string,string[]>(
      key, 
      values2.Concat(names ?? Array.Empty<string>()));
}

No, because syntactically the dic isn't initialized yet within its collection initializer.

This:

var dic = new Dictionary<string, object>
{
    ["foo"] = "Foo",
    ["bar"] = dic["foo"],
};

Yields:

> CS0841 Cannot use local variable 'dic' before it is declared

An alternative would be to specify the contents on beforehand, and reference that:

const string foo = "Foo";
var dic = new Dictionary<string, object>
{
    ["foo"] = foo,
    ["bar"] = foo,
};

Or get rid of the initializer syntax:

var dic = new Dictionary<string, object>();

dic["foo"] = dic["bar"] = "Foo";

You can define a specialized dictionary with an overload Add method as:

public class MyDictionary : Dictionary<string, string[]>
{
    public void Add(params string[] values)
    {
        if (values.Length < 1)
            throw new ArgumentException("At least one string as argument");

        base.Add(values[0], values);
    }
}

and then you can initialize it as:

var dict = new MyDictionary
{
    {"SomeKey", "other value", "another value" },
    {"Some other key", "some other value", "again" }
};

foreach (var item in dict)
{
    Console.WriteLine($"[{item.Key}, [{string.Join(", ",item.Value)}]]");
}
// Output:
// [SomeKey, [SomeKey, other value, another value]]
// [Some other key, [Some other key, some other value, again]]

You may adapt the add method as you need

Other solution:

If you don't want to create e specialized dictionary, you can use Linq's ToDictionary method to initialize the dictionary.
You first initialize a collection of string[] and then crete the dictionary from it.

Here a sample code:

    IReadOnlyDictionary<string, string[]> dictionary
        = new List<string[]> 
        {
            new [] {"KeyA", "ValueA1", "ValueA2" },
            new [] {"KeyB", "ValueB1", "ValueB2", "ValueB3"}
        }.ToDictionary(t=>t[0], t=>t);