Develop Reference

Cannot wrap my head around using a Dictionary with imbedded list such as dictionary<string, list<string>>

trying to add a list object to the dictionary however, I cannot grasp the concept being that you have they key, so you cannot do .add without there being a key violation
working on a shopping list program, I need to add inventory to the customer's cart, remove it from the inventory, then add that to the dictionary.
public static Inventory AddToCart(List<Inventory> Inventory)
{
// this method moves a dvd from inventory to the shopping cart.
int i = 0;
int iInput = 0;
Inventory newCart = null;
if (Inventory.Count > 0)
{
foreach (Inventory obj in Inventory)
{
++i;
Console.WriteLine("[" + i + "] " + obj.ToString());
}
iInput = Validation.GetInt("Please Choose an item to add to cart: ");
Console.Write($"Move item at record: #{iInput - 1} to shopping cart: (y or n)");
string sInput = Console.ReadLine();
if (string.IsNullOrEmpty(sInput))
{
Console.WriteLine("\r\nNo Valid number was chosen: ");
}
else
switch (sInput.ToLower())
{
case "y":
{
newCart = Inventory[iInput - 1];
Inventory.RemoveAt(iInput - 1);
}
break;
case "n":
case null:
case "":
{
Console.WriteLine("\r\nNo Valid number was chosen: ");
}
break;
default:
{
Console.WriteLine("Keeping item in Inventory");
}
break;
}
}
else
{
Console.WriteLine("\nNo records were found in the Shopping Cart");
}
return newCart;
}
This is using only a list, however I need to be able to convert this over to a dictionary with this list imbedded

I'm not sure if I've understood your question but here is some explanation on how to work with dictionaries that contain lists in general.
You have dictionary that consists of a key and a List.
Dictionary<string, List<int>> dictionaryWithList = new Dictionary<string, List<int>>();
If you want to save something into this List you have to create a key-value pair first. This means adding an element to the dictionary containing the key and the list. If you want to have your list filled while adding the key value pair you could do something like this:
List<int> myList = new List<int>();
myList.Add(5);
myList.Add(6);
myList.Add(7);
dictionaryWithList.Add("test", myList);
Now you have a list containing 5, 6 and 7 that you can access with the key "test" inside of the dictionary.
If you want to access the list you just use:
dictionaryWithList["test"]
So if you want to add a new number to the list that has the key "test" then you can use:
dictionaryWithList["test"].Add(42)
If you want to avoid running into Exceptions caused by keys not existing, test if a key exists first:
if(dictionaryWithList.ContainsKey("test"))
Notify me if this hasn't helped you with some further information about your problem :)

string newKey = "NEW KEY";
string firstListElement = "FIRST";
Dictionary<string, List<string>> dict = new Dictionary<string, List<string>>();
if (dict.ContainsKey(newKey)) {
// you need to throw an exception or return some signal to exit function
}
dict.Add(newKey, new List<string>());
dict[newKey].Add(firstListElement);

Adding to the dictionary from a text document C#

I need to read from the text document through =, line by line, and add it to the dictionary. Can you help me please?
using (StreamReader sr = new StreamReader("slovardata.txt"))
{
string _line;
while ((_line = sr.ReadLine()) != null)
{
string[] keyvalue = _line.Split('=');
if (keyvalue.Length == 2)
{
slovarik.Add(keyvalue[0], keyvalue[1]);
}
}
}

You can read all lines of file with File.ReadAllLines and after splitting every line into Key & Value add it into dictionary like the following code:
caution: it may ignore some lines without throwing any exception and it may throw Argument Exception “Item with Same Key has already been added”
var lines = System.IO.File.ReadAllLines("slovardata.txt");
lines.Select(line=>line.Split('='))
.Where(line=>line.Length ==2)
.ToList()
.ForEach(line=> slovarik.Add(line[0],line[1]));
btw the .ForEach method made a lot of garbage (in large lists) and if there is no duplicate keys you can use following:
var slovarik = lines.Select(line=>line.Split('='))
.Where(line=>line.Length ==2)
.ToDictionary(line[0],line[1]);

For simple text file read operation you can use something like this :
Note : Make sure your Keys are unique, otherwise you will get the -
System.ArgumentException: An item with the same key has already been
added.
string[] FileContents = File.ReadAllLines(#"c:\slovardata.txt");
Dictionary<string, string> dict = new Dictionary<string, string>();
foreach (string line in FileContents)
{
var keyvalue = Regex.Match(line, #"(.*)=(.*)");
dict.Add(keyvalue.Groups[1].Value, keyvalue.Groups[2].Value);
}
foreach (var item in dict)
{
Console.WriteLine("Key : " + item.Key + "\tValue : " + item.Value);
}

Values are not being populated into the dictionary <string, string> while I am iterating over a string[] to acquire the <key, value> pair

My idea is to populate a dictionary with string as as key and string as value.
Where x = base64EncodedString of some file that lives in a directory and y = This represents the file name along with the extention so, fileName.extension
I am iterating over a bunch of files that live within a local directory and acquiring the base64string, along with the filename.extension of each file.
In the process I check to see if the value already exists for a given key, and if it does exist, I DO NOT add the key value pair, otherwise I populate the dictionary.
Here is my code below, I am a beginner, and I am trying to work this out.
Dictionary<string, string> d = new Dictionary<string, string>();
string[] attachmentPaths = Directory.GetFiles("someLocalFilePathPopulatedWithFiles");
Byte[] attachmentBytes;
string base64EncodedString;
string attachmentFileName;
foreach (string attachment in attachmentPaths)
{
//Base 64 conversion process
attachmentBytes = File.ReadAllBytes(attachment);
base64EncodedString = Convert.ToBase64String(attachmentBytes);
attachmentFileName = Path.GetFileName(attachment);
if (d.TryGetValue(base64EncodedString, out attachmentFileName))
{
Console.WriteLine("exists");
//trying to get a value for a key that does not exist, on the first iteration, then the compiler jumps to the else{}
}
else
{
Console.WriteLine("!exists");
//Since the <key, value> does not exist, go ahead and populate the dictionary
d.Add(base64EncodedString, attachmentFileName);
}
}
//Print out the key value pair.
//The value is not being printed.
foreach (KeyValuePair<string, string> pair in d)
{
Console.WriteLine("Key: " + pair.Key + " " + "Value: " + pair.Value);
}
The issue is that the value is not being printed.
I have also tried this with simpler code to test the logic and it seemed to work. This seems to work as in I am able to populate the dictionary object with the data that I want, and in the process checking to see if it already exists.
Dictionary<string, string> d = new Dictionary<string, string>();
d.Add("B", "fileB");
d.Add("C", "fileC");
d.Add("D", "fileD");
////we have an empty dicitonary, so lets try to get the value of key that IS not part of dictionary
string val = "fileA";
if (d.TryGetValue("A", out val))
{
Console.WriteLine("exists");
//do not add a key, since the <key ,value> exists
//so the compiler will always jump to the else, {adding a <key, value>}
}
else
{
Console.WriteLine("!exists");
d.Add("A", "fileA");
}
foreach (KeyValuePair<string, string> pair in d)
{
Console.WriteLine("Key: " + pair.Key + " " + "Value: " + pair.Value);
}
I am convinced that there is a difference, but I do not seem to catch it because I am still trying to learn.

d.TryGetValue(base64EncodedString, out attachmentFileName)). This line will clearout the attachmentFileName if it not exists, so in your else part you are adding only null. you need to use another variable here to test if it exists.
Use some temp variable to check the existence
foreach (string attachment in attachmentPaths)
{
//Base 64 conversion process
attachmentBytes = File.ReadAllBytes(attachment);
base64EncodedString = Convert.ToBase64String(attachmentBytes);
attachmentFileName = Path.GetFileName(attachment);
var filename=string.Empty;
if (d.TryGetValue(base64EncodedString, out filename))
{
Console.WriteLine("exists");
//trying to get a value for a key that does not exist, on the first iteration, then the compiler jumps to the else{}
}
else
{
Console.WriteLine("!exists");
//Since the <key, value> does not exist, go ahead and populate the dictionary
d.Add(base64EncodedString, attachmentFileName);
}
}
//Print out the key value pair.
//The value is not being printed.
foreach (KeyValuePair<string, string> pair in d)
{
Console.WriteLine("Key: " + pair.Key + " " + "Value: " + pair.Value);
}

Edit: Complete rewrite after comment by OP.
If the point is to find files where the content is a duplicate of the contents of a different file, then the answer by #Thangadurai should be enough to get past you immediate problem.
I would still suggest that you calculate a digest/hash of the contents of each file, then use a base 64 encoded version of that as you dictionary key. That way you don't have to store the whole content of each and every file in memory while your method is running. Something like this (only very quickly tested):
Dictionary<string, string> d = new Dictionary<string, string>();
string[] attachmentPaths = Directory.GetFiles("c:\\temp");
System.Security.Cryptography.SHA1Managed sha1 = new System.Security.Cryptography.SHA1Managed();
byte[] oneFileHash = null;
foreach (string attachment in attachmentPaths)
{
using (FileStream oneFileStream = File.OpenRead(attachment))
{
oneFileHash = sha1.ComputeHash(oneFileStream);
}
if (oneFileHash == null)
continue;
string base64EncodedHash = Convert.ToBase64String(oneFileHash);
string attachmentFileName = Path.GetFileName(attachment);
if (d.ContainsKey(base64EncodedHash))
{
Console.WriteLine("exists");
//trying to get a value for a key that does not exist, on the first iteration, then the compiler jumps to the else{}
}
else
{
Console.WriteLine("!exists");
//Since the <key, value> does not exist, go ahead and populate the dictionary
d.Add(base64EncodedHash, attachmentFileName);
}
}
foreach (KeyValuePair<string, string> pair in d)
{
Console.WriteLine("Key: " + pair.Key + " " + "Value: " + pair.Value);
}
If I were you I would not waste any thought on the relative performance of ContainsKey and TryGetValue. Neither of them will be the bottleneck here. If you want to check if the dictionary contains a certain key already, go ahead and use the method that most clearly signals that it's doing that for you.
Note: There is a theoretical chance that two files with different contents will end up with the same hash. The chance that this will happen is vanishingly small. So small that you can in practise ignore it completely...

Deleting all entries in a Dictionary c# WPF

I have a Dictionary which is storing members of a Skilodge and I want a method to delete all members. At the moment, it only seems to be removing one. Here is the method I tried:
public void DeleteAll()
{
for (int i = 0; i < Skiers.Count; i = i + 1)
{
string iString = i.ToString();
Skiers.Remove(iString);
}
}

use Clear method check this link
Skiers.Clear()

You can use Skiers.Clear(); for removing all existing values of the given Dictionary, And you can use Skiers= new Dictionary<T,T>() to get a fresh Dictionary(new instance);
Dictionary.Clear Method () will Removes all keys and values from the Dictionary.
You can try Conditional Remove also, Let the Dictionary may defined and initialized as like the following:
Dictionary<string, String> dictSample = new Dictionary<string, string>();
dictSample.Add("a", "value 1");
dictSample.Add("b", "value 1");
dictSample.Add("c", "value 12");
dictSample.Add("d", "value 10");
dictSample.Add("e", "value 1");
And you had a requirement of removing some specific items those are having value 1 in its value part, then you can use the following code for removing them:
var removable = dictSample.Where(x => x.Value == "value 1").Select(x => x.Key).ToList();;
foreach (var dictItem in removable)
{
dictSample.Remove(dictItem);
}

c#: How to iterate through a List<>, that is a value in a dictionary?

Right now I have a dictionary being populated with an account as key, and a List as value. I believe my code is working to populate it. But my next step is to iterate through that List associated with a particularly key and do stuff with the list (get sums for each field). I am not that familiar with dictionaries so I am not sure how to access the values and perform an action. I would like to do this summation and print it out in my for each loop, when I exit the while loop.
1) If I could figure out how to access each field in DataRecords (inside the foreach loop), I could likely figure out how to do the summation.
2) Also looking for a way to print the values so I can see if it is even populated correctly.
static void Main(string[] args)
{
Dictionary<string, List<DataRecord>> vSummaryResults = new Dictionary<string, List<DataRecord>>();
while (!r.EndOfStream)
{
if (control == "1")
{
// Need to add List<Datarecords> into dictionary...
if (vSummaryResults.ContainsKey(records.account))
{
vSummaryResults[records.account].Add(records);
}
else
{
vSummaryResults.Add(records.account, new List<DataRecord>());
vSummaryResults[records.account].Add(records);
}
}
}
foreach (List<DataRecord> rec in vSummaryResults.Values)
{
Console.WriteLine(rec.); dictionary.
}
vWriteFile.Close();
Console.ReadLine();
}
Here is my DataRecord class that I am using as the object in the List.
public class DataRecord
{
fields.....
}

For iterations over a dictionary, we use KeyValuePair:
foreach (KeyValuePair<string, List<DataRecord>> kvp in vSummaryResults)
{
string key = kvp.Key;
List<DataRecord> list = kvp.Value;
Console.WriteLine("Key = {0}, contains {1} values:", key, list.Count);
foreach (DataRecord rec in list)
{
Console.WriteLine(" - Value = {0}", rec.ToString()); // or whatever you do to put list value on the output
}
}

You need another loop inside the first to get values in your list.
foreach (List<DataRecord> rec in vSummaryResults.Values)
{
foreach(DataRecord data in rec)
{
Console.WriteLine(data .YourProperty);
}
}
If you know the key:
foreach (List<DataRecord> rec in vSummaryResults[key])
{
foreach(DataRecord data in rec)
{
Console.WriteLine(data .YourProperty);
}
}

I made an example with a simple situation. Its a list of strings, but you can do the object.ToString() to get some tekst;
To loop over the list contained by the key you need to iterate over that list again that is what the 2nd foreach does.
Dictionary<string, List<string>> dictionary = new Dictionary<string, List<string>>();
List<String> ls = new List<string>();
ls.Add("item1");
ls.Add("item2");
dictionary.Add("it1", ls);
dictionary.Add("it2", ls);
foreach (var item in dictionary)
{
foreach(var it in item.Value)
{
Console.WriteLine(it);
}
}

You have a dictionary
Dictionary<string, List<DataRecord>> vSummaryResults = new Dictionary<string, List<DataRecord>>();
You could do a
foreach (List<DataRecord> recs in vSummaryResults.Values)
{
foreach (DataRecord rec in recs)
Console.WriteLine(rec.Something);
}
You haven't specified what DataRecord looks like, but you would get a list of list. There's probably a lovely Linq expression that could do the same.

I understand it from reading your code, you have a dictionary where each key has a list of type DataRecord.
With your current loop
foreach (List<DataRecord> rec in vSummaryResults.Values)
{
Console.WriteLine(rec.); dictionary.
}
You looped through each List of type DataRecord. To access the data stored in each object in each list you will need to include another foreach loop to loop through the objects in the list.
foreach (var rec in vSummaryResults.Values)
{
// At this point we have access to each individual List<DataRecord>
foreach(var SingleDataRecordObj in rec)
Console.WriteLine(ingleDataRecordObj.membervariablename)
//From here we are able to list the individual variable member names of values that are in the DataRecord data type, showing all of the information in each list that is stored in the values of the dictionary
}
You can't modify the data in the foreach loop, but you could add them a more simple data structure to perform whatever commutation you wanted etc.

Here is the code for exactly what I needed to do. Working the way I need it to now, thanks for everyone's help.
int iSumOpen = 0;
foreach (KeyValuePair<string, List<DataRecord>> kvp in vSummaryResults)
{
string key = kvp.Key; //assigns key
List<DataRecord> list = kvp.Value; //assigns value
Console.WriteLine("Key = {0}", key);
iSumOpen = 0;
foreach (DataRecord rec in list)
{
if (vSummaryResults.ContainsKey(key))
{
iSumOpen += rec.open;
}
else
{
vSummaryResults.Add(key, list);
}
}
Console.WriteLine(iSumOpen);
}