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Cumulatively add values to Dictionary

I am trying to add values to a dictionary as they get determined based on certain conditions. The app has to loop through each line and once a certain condition has been met then a value must be added to the dictionary. Here is the code that is task with looping through the lines and determine values to be added.
foreach (var line in this.FileLines)
{
count++;
string[] bits = line.Split(',');
fineNumber = bits[0].Trim();
int length = bits.Length;
if (length == 9)
{
//other processing gets done here, code not included as its of no interest for this question
}
else
{
//AddErrorFinesToFile(line, fineNumber);
AddFinesToDictonary(fineNumber, line);
continue;
}
}
Then below is the actual method signature and its code, in this method I am simply trying to add values to the dictionary as they come.
public Dictionary<string, string> AddFinesToDictonary(string fineNumber, string errorLine)
{
Dictionary<string, string> erroredLines = new Dictionary<string, string>();
erroredLines.Add(fineNumber, errorLine);
return erroredLines;
}
The only problem that seems to arise here is, only the latest value gets added to the dictionary, meaning the previous added value gets overwritten.

Make erroredLines as global scope.
Dictionary<string, string> erroredLines = new Dictionary<string, string>();
foreach (var line in this.FileLines)
{
count++;
string[] bits = line.Split(',');
fineNumber = bits[0].Trim();
int length = bits.Length;
if (length == 9)
{
//other processing gets done here, code not included as its of no interest for this question
}
else
{
//AddErrorFinesToFile(line, fineNumber);
AddFinesToDictonary(fineNumber, line);
continue;
}
}
public void AddFinesToDictonary(string fineNumber, string errorLine)
{
erroredLines.Add(fineNumber, errorLine);
// return erroredLines;
}
And also no need to return erroredLines dictionary.

What about this;
Dictionary<string, string> erroredLines = new Dictionary<string, string>();
foreach (var line in this.FileLines)
{
count++;
string[] bits = line.Split(',');
fineNumber = bits[0].Trim();
int length = bits.Length;
if (length == 9)
{
//other processing gets done here, code not included as its of no interest for this question
}
else
{
erroredLines.Add(fineNumber, line);
continue;
}
}
after foreach you can use erroredLines dictionary.

The reason is every time you add data to the Directory you create a new one instead of adding data to the exists one
There are two choices you could make:
make a Dictionary out of the function
pass the Dictionary as an out ref to the function
#Hameed Syed 's answer has already given the first one (option 1).
Here is how you could pass the Dictionary as a ref parameter (out) to the function (option 2):
public void AddFinesToDictonary(out Dictionary<string,string>dict, string fineNumber, string errorLine)
{
dict.Add(fineNumber, errorLine);
}

Check if an item exist in the dictionary and remove it from the dictionary in C# [duplicate]

This question already has answers here:
Remove Item in Dictionary based on Value
(6 answers)
Closed 9 years ago.
The question should be clear from the title itself. I need to check if an item exist in the dictionary and remove it from the dictionary in C#. The only catch is that i have to do this using only the value item and not the key.
The declaration is as below:
IDictionary<string, myCustomClassObject> clients = new IDictionary<string, myCustomClassObject>();
Now i fill in the dictionary by:
clients["key"] = myCustomClassObject1;
Now how can i find and remove this item myCustomClassObject1 from my Dictionary. I only want to use the value item and not the key
Is this doabale...if so please guide...
regards
Edit: Thank you all....got valuable comments...probably have some thinking to do ...thanks

It depends on how you need it to perform. If you can accept O(N) performance, you could just do something like:
foreach(var pair in clients) {
if(pair.Value == expected) {
clients.Remove(pair.Key);
break;
}
}
However, if you need faster you would need two dictionaries - one the reverse of the other (i.e. keyed by the instances). So when adding, you would do:
clientsByKey.Add(key, value);
clientsByValue.Add(value, key);
so you can do (to remove-by-value):
string key;
if(clientsByValue.TryGetValue(value, out key)) {
clientsByValue.Remove(value);
clientsByKey.Remove(key);
}
or similarly (to remove-by-key):
Foo value;
if(clientsByKey.TryGetValue(key, out value)) {
clientsByValue.Remove(value);
clientsByKey.Remove(key);
}

It's not very efficient to search a dictionary by it's values. However, you can use Linq to find all entries with a given value.
IEnumerable<KeyValuePair<string, myCustomClassObject>> pairs = clients
.Where(entry => entry.Value.Equals(myCustomClassObject1)).ToList();
foreach (KeyValuePair<string, myCustomClassObject> kv in pairs)
clients.Remove(kv.Key);

This should do it. It removes all clients having a given value.
while (clients.ContainsValue(myCustomClassObject1))
clients.Remove(clients.Where(x => x.Value == myCustomClassObject1).FirstOrDefault().Key);
Or create a new dictionary without the values you want removed
clients = clients.Where(x => x.Value != myCustomClassObject1).ToDictionary(k => k.Key, v => v.Value);

If the collection only contains one item with the value to be removed then you can use one of the other answers here, which will work just fine.
However, if your collection can have multiple items with the same value then you need to be careful.
You cannot modify a collection while iterating over it, so you will need to find the keys of all the items that you want to remove in one loop and put them in a list, and then iterate over that list in a separate loop to delete the items.
For example:
using System;
using System.Collections.Generic;
using System.Linq;
namespace Demo
{
class Program
{
void run()
{
var dict = new Dictionary<string, int>
{
{"Key1", 1},
{"Key2", 2},
{"Key3", 3},
{"Key4", 2},
{"Key5", 4}
};
int valueToRemove = 2;
var keysToRemove = (from element in dict
where element.Value == valueToRemove
select element.Key).ToList();
foreach (var key in keysToRemove)
dict.Remove(key);
foreach (var element in dict)
Console.WriteLine("Key = {0}, Value = {1}", element.Key, element.Value);
}
static void Main(string[] args)
{
new Program().run();
}
}
}

Use,
Following will remove only first matching value
client newClient = new client();
foreach(KeyValuePair<string, client> client in clients) {
if(client.value.equals(newClient)) {
clients.remove(client.key);
break;
}
}
Or if you want to remove all matching values,
foreach(var client in clients.Where(kvp => kvp.Value == newClient).ToList()) {
clients.Remove(client.Key);
}

How to avoid run time error while working with dictionary

I have a piece of code that represent Dictionary and search key array.
Dictionary<string, string> items = new Dictionary<string, string>()
{
{"1","Blue"},
{"2","Green"},
{"3","White"}
};
string[] keys = new[] { "1", "2", "3", "4" };
How to safely avoid the run time error when i pass a key that is not present in dictionary?

How to safely avoid the run time error when i pass a key that is not present in dictionary?
You haven't shown how you're currently trying to do it, but you can use Dictionary<,>.TryGetValue:
foreach (string candidate in keys)
{
string value;
if (items.TryGetValue(candidate, out value))
{
Console.WriteLine("Key {0} had value {1}", candidate, value);
}
else
{
Console.WriteLine("No value for key {0}", candidate);
}
}

Use either ContainsKey or TryGetValue to check the existence of a key.
string val = string.Empty;
foreach (var ky in keys)
{
if (items.TryGetValue(ky, out val))
{
Console.WriteLine(val);
}
}
or
foreach (var ky in keys)
{
if (items.ContainsKey(ky))
{
Console.WriteLine(items[ky]);
}
}
Though TryGetValue is faster than ContainsKey use it when you want to pull the value from dictionary.if you want to check the existence of key use ContainsKey.

Making a List<string> from Dictionary<string, string>

I was wondering if it were possible to make a list from the dictionary values where the key is a specified value?
The dictionary would like this:
Sidcup - DPC1
Sidcup - DPC2
Blackheath - DPC3
Blackheath - DPC4
Bexleyheath - DPC5
In fact, I'm not entirely implementing a Dictionary as above is a good idea. Here is its implementation:
DataSet ds = EngineBllUtility.GetDPCsForImportFile(connectionString, fileID);
if (ds.Tables.Count > 0)
{
DataTable dtDPCs = EngineBllUtility.GetDPCsForImportFile(connectionString, fileID).Tables[0];
Dictionary<string, string> preliminaryList = new Dictionary<string, string>();
if (dtDPCs.Columns.Contains("DPCNumber") && dtDPCs.Columns.Contains("BranchName"))
foreach (DataRow dataRow in dtDPCs.Rows)
{
preliminaryList.Add(dataRow["BranchName"].ToString(), dataRow["DPCNumber"].ToString());
}
I have the following code: (Excuse the last line, its just so you have an idea of what I'm trying to do).
foreach (string branch in branchNames)
{
string subfolder = System.IO.Path.Combine(saveLocation, branch);
System.IO.Directory.CreateDirectory(subfolder);
List<string> certificateList = new List<string>();
certificateList.Add(DPCNumber in preliminaryList where Key = branch);
}
In the above the branch is the key from the Dictionary. I need to iterate through because it needs to create a new folder and then do something with the certificateList I am creating.

Sure:
private static void TestZip()
{
Dictionary<string, string> stringstringdic = new Dictionary<string, string>();
stringstringdic.Add("1", "One");
stringstringdic.Add("2", "Two");
stringstringdic.Add("3", "Three");
stringstringdic.Add("4", "Four");
stringstringdic = stringstringdic.Where(pair => pair.Key != "1")
.ToDictionary(pair => pair.Key, pair => pair.Value);
List<string> stringlist = stringstringdic.Keys.Concat(stringstringdic.Values).ToList();
foreach (string str in stringlist)
{
Console.WriteLine(str);
}
}
//Output:
//2
//3
//4
//Two
//Three
//Four
Of course, you'll have to change the Where clause to reflect your real need.
If I understood you right, it's like .Where(pair => pair.Key == branch)

If I understand you correctly you want to add the value based on a key to a separate List?
certificateList.Add(preliminaryList[branch])
This is simplified as I really need to see the declaration of preliminaryList to know how DPCNumber fits into all of it. Could it be...
certificateList.Add(preliminaryList[branch].ToString())

To simply create a list of keys you can do the following.
var dictionary = new Dictionary<string, string>();
dictionary.Add("key1", "value1");
dictionary.Add("key2", "value2");
dictionary.Add("key3", "value3");
dictionary.Add("key4", "value4");
dictionary.Add("key5", "value5");
var list = dictionary.Keys.ToList();
This should give you a list with values "key1", "key2", "key3", "key4", "key5".
You can put a where clause in to filter out certain keys. The following gives all keys which contain a "2" (random example), resulting in just "key2".
var filteredList = dictionary.Keys.Where(key => key.Contains("2")).ToList();
Edit:
To get a value given a specific key.
string value = dictionary["key1"];
Note, the key is a dictionary must be unique, so for a given key you will only ever get a single value back and not a list of values.

Is this an efficient code for Multi Key Dictionary in a Method Body?

I just want to ask if:
The code below is efficient?
Is there a better way to handle this?
How to code if additional values for tablename/fieldname pair are needed?
We need to use a multi-key dictionary that contains something like (TableName, FieldName, FieldValue).
I searched some answer but the ones I found so far are not applicable to our setup. We are using 3.5 so no Tuple available yet. We are also integrating this script logic with an application that only allows coding "inside" a method body, so we are limited and cannot create a separate class/structure, etc. Our set up is C#/VS 2010.
Any help is appreciated. Thanks in advance!
Dictionary<string, Dictionary<string, string>> tableList = new Dictionary<string, Dictionary<string, string>>();
Dictionary<string, string> fieldList = new Dictionary<string, string>();
// add fields to field list, then add the field lists to the corresponding table list
// clear field list for next table
// values are just hardcoded here to simplify, but is being read from actual objects in the application
fieldList.Add("Field1", "abc");
fieldList.Add("Field2", "def");
fieldList.Add("Field3", "ghi");
fieldList.Add("Field4", "jkl");
tableList.Add("Table1", new Dictionary<string, string>(fieldList));
fieldList.Clear();
fieldList.Add("Field1", "xyz");
fieldList.Add("Field2", "uvw");
fieldList.Add("Field3", "rst");
tableList.Add("Table2", new Dictionary<string, string>(fieldList));
fieldList.Clear();
fieldList.Add("Field1", "123");
fieldList.Add("Field2", "456");
tableList.Add("Table3", new Dictionary<string, string>(fieldList));
fieldList.Clear();
// Display tables and corresponding fields
foreach (KeyValuePair<string, Dictionary<string, string>> fieldList4 in tableList)
{
foreach (KeyValuePair<string, string> fieldList5 in fieldList4.Value)
{
txtMessage.Text = txtMessage.Text + "\r\nTable=" + fieldList4.Key + ", Field=" + fieldList5.Key + " - " + fieldList5.Value;
}
}
// Try to find tables and fields in the lists, and list the value if found
string tableToFind = "Table2";
string fieldToFind = "Field2";
Dictionary<string, string> tableFields = new Dictionary<string, string>();
if (tableList.Keys.Contains(tableToFind) == true)
{
txtMessage.Text = txtMessage.Text = "\r\nTable=" + tableToFind + " exist in table list";
tableList.TryGetValue(tableToFind, out tableFields);
if (tableFields.Keys.Contains(fieldToFind) == true)
{
foreach(KeyValuePair<string, string> fieldData in tableFields)
{
if (fieldData.Key == fieldToFind)
{
txtMessage.Text = txtMessage.Text + "\r\nTable=" + tableToFind + ", Field=" + fieldData.Key +
" with value=" + fieldData.Value + " exist in table list";
break;
}
}
}
}

You can use the compiler to create a composite key for you: Using anonymous types.
var dictionary = new Dictionary<Object, int>();
dictionary.Add(new{Text="A", Number=1}, 1);
dictionary.Add(new{Text="A", Number=2}, 3);
dictionary.Add(new{Text="B", Number=1}, 4);
dictionary.Add(new{Text="B", Number=2}, 5);
var x = dictionary[new{Text="B", Number=2}];
C# will implement Equals and GetHashcode based on your fields. Thus you do get a key which will behave as you would expect.

There's a whole slew of problems and inefficiencies in your code.
If you're going to create multiple dictionaries, create the dictionaries directly. Don't use a separate instance to fill the values and copy from.
Never use string concatenation in a loop like that. Use a StringBuilder or other similar mechanism to build up your strings. You already have your values in a collection so using String.Join() in conjunction with LINQ would clean that up.
Your approach to get values from the dictionary is awkward to say the least. Normally you'd use TryGetValue() alone to attempt to read the key. Your code uses it incorrectly. If you are going to check if the key exists in the dictionary (using Contains()), then there's no point in using TryGetValue(). To make things worse, you did this then searched for the key manually in the inner dictionary by iterating through the key value pairs.
The typical pattern looks like this:
DictValueType value;
if (myDict.TryGetValue(key, out value))
{
// key was in the dictionary, the value is stored in the `value` variable
}
The code you have could be written much much more efficiently like this:
var tableList = new Dictionary<string, Dictionary<string, string>>
{
{ "Table1", new Dictionary<string, string>
{
{ "Field1", "abc" },
{ "Field2", "def" },
{ "Field3", "ghi" },
{ "Field4", "jkl" },
}
},
{ "Table2", new Dictionary<string, string>
{
{ "Field1", "xyz" },
{ "Field2", "uvw" },
{ "Field3", "rst" },
}
},
{ "Table3", new Dictionary<string, string>
{
{ "Field1", "123" },
{ "Field2", "456" },
}
},
};
// Display tables and corresponding fields
txtMessage.Text = String.Join("\r\n",
tableList.SelectMany(table =>
table.Value.Select(fieldList =>
String.Format("Table={0}, Field={1} - {2}",
table.Key, fieldList.Key, fieldList.Value)
)
).ToArray()
);
// (I hope you have this in a separate method)
// Try to find tables and fields in the lists, and list the value if found
string tableToFind = "Table2";
string fieldToFind = "Field2";
var builder = new StringBuilder(txtMessage.Text); // mostly useful if you have a
// lot of different strings to add
Dictionary<string, string> foundTable;
if (tableList.TryGetValue(tableToFind, out foundTable))
{
builder.AppendLine()
.Append("Table=" + tableToFind + " exist in table list");
string foundField;
if (foundTable.TryGetValue(fieldToFind, out foundField))
{
builder.AppendLine()
.AppendFormat("Table={0}, Field={1} with value={2} exist in table list",
tableToFind, fieldToFind, foundField);
}
}
txtMessage.Text = builder.ToString();
Nested dictionaries aren't a bad thing, it's a nice way to organize hierarchies of keys and values. But to keep it maintainable, you generally should encapsulate everything within another class providing methods to manipulate the data without having to manage the dictionaries directly. You can make it both efficient and maintainable. How to implement this is an exercise left to you.

I don't think so many dictionaries would be 'efficient'.
I think the best way would be to add values into the same dictionary multiple times - assuming you want to be able to index them according to one of the indicies (not all):
dictionary.Add("FField1", "xxx");
dictionary.Add("TTable1", "xxx");
Otherwise use a joining character (like '\0') if you want to index them according to all the indicies together.
dictionary.Add("Table1\0Field1", "xxx");