Processing a C# Dictionary using LINQ
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Processing a C# Dictionary using LINQ
提问by Sriram B
How do I write the "// Display using Foreach" loop implementation using LINQ Lambda Expression / Statemene Expression?
How do I write the "// Display using Foreach" loop implementation using LINQ Lambda Expression / Statemene Expression?
I want to simplify my development and avoid nested foreach loops as much as possible. I am trying to include more logic with in the second foreach statement and I want to use Lambda / Statement expression.
I want to simplify my development and avoid nested foreach loops as much as possible. I am trying to include more logic with in the second foreach statement and I want to use Lambda / Statement expression.
internal class Program
{
internal class Country
{
public string CountryName { get; set; }
public int CountryCode { get; set; }
}
static void Main(string[] args)
{
List<Country> countries = new List<Country>()
{
new Country{CountryName = "India", CountryCode=1},
new Country{CountryName = "Andaman Nicobar", CountryCode=1},
new Country{CountryName = "United States of America", CountryCode=2},
new Country{CountryName = "Alaska", CountryCode=2},
new Country{CountryName = "Hawaii", CountryCode=2},
new Country{CountryName = "United Kingdom", CountryCode=3},
new Country{CountryName = "Australia", CountryCode=4}
};
Dictionary<int, List<Country>> countriesDictionary = new Dictionary<int, List<Country>>();
foreach (Country country in countries)
{
if (!countriesDictionary.ContainsKey(country.CountryCode))
countriesDictionary.Add(country.CountryCode, new List<Country>());
countriesDictionary[country.CountryCode].Add(country);
}
// Display using Foreach
foreach (int key in countriesDictionary.Keys)
{
List<Country> dCountries = countriesDictionary[key];
foreach (Country country in dCountries)
{
if (country.CountryCode.Equals(key))
{
Console.WriteLine(country.CountryName);
}
}
Console.WriteLine();
}
Console.ReadLine();
}
Please suggest.
Please suggest.
采纳答案by Sergey Berezovskiy
If you want to group countries by code, then you don't need two dictionaries. Use Enumerable.GroupBy
If you want to group countries by code, then you don't need two dictionaries. Use Enumerable.GroupBy
foreach(var codeGroup in countries.GroupBy(c => c.CountryCode))
{
foreach(var country in codeGroup)
Console.WriteLine(country.CountryName);
Console.WriteLine();
}
Or just use your countriesDictionary(it already has countries grouped by code):
Or just use your countriesDictionary(it already has countries grouped by code):
foreach(var kvp in countriesDictionary)
{
foreach(var country in kvp.Value)
Console.WriteLine(country.CountryName);
Console.WriteLine();
}
回答by Theraot
This is another alternative:
This is another alternative:
countriesDictionary.ToList().ForEach
(
pair =>
{
pair.Value.ForEach(country => Console.WriteLine(country.CountryName));
Console.WriteLine();
}
);
Also, this one based on Romoku's Answer(the answer was removed):
Also, this one based on Romoku's Answer(the answer was removed):
var countriesDictionary = countries.ToLookup(x => x.CountryCode, x => x);
foreach(var countryGroup in countriesDictionary)
{
foreach(var country in countryGroup)
{
Console.WriteLine(country.CountryName);
}
Console.WriteLine();
}
回答by Jamie - Fenrir Digital Ltd
Or just make it very easy... as already mentioned, you're already grouping by Country code...
Or just make it very easy... as already mentioned, you're already grouping by Country code...
foreach (var country in countriesDictionary.SelectMany(pair => pair.Value))
{
Console.WriteLine(country.CountryName);
}
回答by ígor
I will use a extension to do it.
I will use a extension to do it.
static class CountryExtension
{
public static void WriteCountriesGroupyCountryCode(this IEnumerable<Country> list)
{
int currentCountry=int.MinValue;
list.OrderBy(c => c.CountryCode).ThenBy(c=>c.CountryName).ToList().ForEach(c =>
{
if (currentCountry == int.MinValue)
{
currentCountry = c.CountryCode;
}
else if (currentCountry != c.CountryCode)
{
Console.WriteLine();
currentCountry = c.CountryCode;
}
Console.WriteLine(c.CountryName);
});
}
}
回答by terrybozzio
One way could be like this,avoiding the first foreach with GroupBy,the just 1 foreach logic to print each country name with specified code:
One way could be like this,avoiding the first foreach with GroupBy,the just 1 foreach logic to print each country name with specified code:
Dictionary<int, List<Country>> countriesDictionary = countries.GroupBy(g => g.CountryCode).ToDictionary(k => k.Key, k => k.ToList());
foreach (int key in countriesDictionary.Keys)
{
Console.WriteLine("****Countries with code {0}****",key);
int count = 0;
while (count < countriesDictionary[key].Count)
{
Console.WriteLine(countriesDictionary[key][count].CountryName);
count++;
}
Console.WriteLine();
}
Console.ReadLine();
回答by MadHenchbot
Though you probably have enough answers for the time being, this LINQ will compress your dictionary into a list of country names, allowing an easy foreach to display them.
Though you probably have enough answers for the time being, this LINQ will compress your dictionary into a list of country names, allowing an easy foreach to display them.
List<string> countryNames = countriesDictionary.SelectMany(
pair=>pair.Value.Where(
country=>country.CountryCode == pair.Key
).Select(x=>x.CountryName)).ToList();
foreach (var name in countryNames)
Console.WriteLine(name);
But the way your Dictionary is set up, the key should always match the country codes in the value, correct?
But the way your Dictionary is set up, the key should always match the country codes in the value, correct?
