I generally use a foreach loop to iterate through Dictionary.
Dictionary<string, string> dictSummary = new Dictionary<string, string>();
In this case I want to trim the entries of white space and the foreach loop does however not allow for this.
foreach (var kvp in dictSummary)
{
kvp.Value = kvp.Value.Trim();
}
How can I do this with a for loop?
for (int i = dictSummary.Count - 1; i >= 0; i--)
{
}
what about this?
for (int i = dictSummary.Count - 1; i >= 0; i--) {
var item = dictSummary.ElementAt(i);
var itemKey = item.Key;
var itemValue = item.Value;
}
KeyValuePair<TKey, TValue> doesn't allow you to set the Value, it is immutable.
You will have to do it like this:
foreach(var kvp in dictSummary.ToArray())
dictSummary[kvp.Key] = kvp.Value.Trim();
The important part here is the ToArray. That will copy the Dictionary into an array, so changing the dictionary inside the foreach will not throw an InvalidOperationException.
An alternative approach would use LINQ's ToDictionary method:
dictSummary = dictSummary.ToDictionary(x => x.Key, x => x.Value.Trim());
You don't need to use .ToArray() or .ElementAt(). It is as simple as accessing the dictionary with the key:
dictSummary.Keys.ToList().ForEach(k => dictSummary[k] = dictSummary[k].Trim());
Related
From this example: https://stackoverflow.com/a/27034916/1312879
I have this kind of dictionary
Dictionary<int, List<string>> fileList = new Dictionary<int, List<string>>();
The example prints "fijo", "Frigy", "lijo", "liji", "vimal", "vilma"
How can I print "fijo", "lijo", "vimal", "Frigy", "liji", "vilma", I mean all the [0] position of each list, the [1] position and so on
You can code pretty much as you said:
foreach (var kvp in fileList)
{
Console.WriteLine (kvp.Value[0]);
}
foreach (var kvp in fileList)
{
Console.WriteLine (kvp.Value[1]);
}
And if there is more item in the inner list, you might want to use a loop for that, assuming they all have the same length:
for (int i = 0; i < fileList.First().Value.Count; i++)
{
foreach (var kvp in fileList)
{
Console.WriteLine (kvp.Value[i]);
}
}
Here you go:
for(int i=0; i < fileList.Values.Max(v=> v==null ? 0 : v.Length); i++)
{
foreach(var keyValuePair in fileList)
{
if(kvp.Value == null || i >= kvp.Value.Length)
continue;
Console.WriteLine(kvp.Value[i]);
}
}
However, I wonder reason behind traversing data structure in columnar fashion when it was created based on rows (or vice versa). You may be better off using different data structure that can serve all use cases.
I'm iterating over a dictionary Dictionary<double, int> diametersAndQuantities and the dictionary is modified. Obviously I'm getting an exception that the collection has been modified. How can I prevent this from happening?
foreach (var diametersAndQuantity in diametersAndQuantities)
{
// some operations here
// update
diametersAndQuantities[db] = n;
}
You can create a temporary list of the KeyValuePairs to iterate over and still update the dictionary.
foreach (var diametersAndQuantity in diametersAndQuantities.ToList())
{
// some operations here
// update
diametersAndQuantities[diametersAndQuantity.Key] = n;
}
you can use the ToList() to get the enumeration to be evaluated
similar to accepted answer - maybe a little faster
should use less memory
Dictionary<int, int> dic = new Dictionary<int, int>() { { 1, 2 }, { 2, 3 }, { 3, 2 } };
foreach (int value in dic.Values)
Debug.WriteLine(value);
foreach (int key in dic.Keys.ToList())
dic[key] = 12;
foreach (int value in dic.Values)
Debug.WriteLine(value);
Debug.WriteLine("done");
I'm working with Open XML & I have a IDictionary<String, List<OpenXmlCompositeElement>> structure. I want to work with the List part of the structure but this.map.Values tries to wrap it in an ICollection. How can I get the List part from my structure?
public List<OpenXmlCompositeElement> MapData()
{
//this does not work
return this.map.Values;
}
Since it is a dictionary, it expects you to tell from which key you want the value.
So this would be the code you need, where yourKey is the key you want to retrieve:
public List<OpenXmlCompositeElement> MapData()
{
return this.map["yourKey"];
}
If you have no interest in the key, and the dictionary is just a dictionary because the serializer says so, you could get the first item for example like this:
public List<OpenXmlCompositeElement> MapData()
{
return this.map.Values.First();
}
You can either loop through the dictionary and use the value you would like, or access the List directly using the key (in this case it's a string)
IDictionary<String, List<OpenXmlCompositeElement>> myDictionary;
List<OpenXmlCompositeElement> myList = myDictionary["myKey"];
Where myKey is available in the dictionary.
Alternatively you can loop through
foreach (var item in myDictionary)
{
var key = item.Key;
var value = item.Value
// You could then use `key` if you are unsure of what
// items are in the dictionary
}
Assuming this is your dictionary...
IDictionary<string, List<OpenXmlCompositeElement>> items = ...;
Get a specific List by key...
List<OpenXmlCompositeElement> list = items["key"];
Get the first list in the dictionary...
List<OpenXmlCompositeElement> list = items.Values.First();
Concatenate all lists in the dictionary into a single list...
List<OpenXmlCompositeElement> list = items.SelectMany(o => o).ToList();
foreach(KeyValuePair<string, List<OpenXmlCompositeElement>> kvp in IDictionary)
{
string key = kvp.key
List<OpenXmlCompositeElement> list = kvp.Value;
foreach(OpenXmlCompositeElement o in list)
{
Do anything you need to your List here
}
}
I am working with dictionaries as well, so here is a real example that I am currently working with:
foreach(KeyValuePair<string, List<DataRecords>> kvp in vSummaryResults)
{
string sKey = kvp.Key;
List<DataRecords> list = kvp.Value;
string[] vArr = sKey.Split(',');
int iTotalTradedQuant = 0;
double dAvgPrice = 0;
double dSumQuantPrice = 0;
double dQuantPrice = 0;
double dNumClose = 0;
foreach (DataRecords rec in list)
{
if(vSummaryResults.ContainsKey(sKey))
{
iTotalTradedQuant += rec.iQuantity;
dQuantPrice = rec.iQuantity * rec.dInputTradePrice;
dSumQuantPrice += dQuantPrice;
dAvgPrice = dSumQuantPrice / iTotalTradedQuant;
dNumClose = rec.dNumericClosingPrice;
}
else
{
vSummaryResults.Add(sKey, list);
//dNumClose = rec.dNumericClosingPrice;
}
For my homework, I have to use a SortedList to count words in a List with SortedList taking each entry and sorting it in alphabetical order before inserting. When it comes to display the data to the user, the data displayed should be displayed with sorting according to value instead of key.
Below is my attempt at this but I am getting 3 errors and I don't know how to resolve it. I am not allowed to use LINQ for this.
List<string> words = new List<string>(); <--- Already populated
This is my code of this implementation and I get 3 errors:
SortedList<string, int> d = new SortedList<string, int>();
bool InsideOfList = false;
foreach (string word in words)
{
InsideOfList = false;
foreach (KeyValuePair<string, int> keyvalPair in d)
{
if (keyvalPair.Key == word)
{
keyvalPair.Value += 1;
InsideOfList = true;
}
}
if (InsideOfList == false)
{
d.Add(word,1);
}
}
//Now instead of sorting by key I want to sort by value instead
SortedList<int, string> tempSortList = new SortedList<int, string>();
foreach (KeyValuePair<string, int> keyvalPair in d)
{
//trying to swap the value of previous SortedList with the Key of the new SortedList
tempSortList.Add(keyvalPair.Value, keyvalPair.Key);
}
for (int i = 0; i < 20; i++)
{
Console.WriteLine("\t{0}:\t{1}", tempSortList.GetKey(i), tempSortList.GetByIndex(i));
}
Here are my errors:
Property or indexer 'System.Collections.Generic.KeyValuePair<string,int>.Value' cannot be assigned to -- it is read only
'System.Collections.Generic.SortedList<int,string>' does not contain a definition for 'GetKey'
'System.Collections.Generic.SortedList<int,string>' does not contain a definition for 'GetByIndex'
You are confusing two things here. One is SortedList() and other is SortedList().
GetKey and GetKeyList are not present in SortedList(). You can use this instead of GetKey
tempSortList.ElementAt(index); // This will return you a KeyValuePair.
And for the first error you cannot assign value keyvalPair.Value has only getter. So you cannot set its value by doing += 1.
This is not quite good. Needs some improvement but it will work.
for (int i = 0; i < d.Count; i++)
{
if (d.ElementAt(i).Key == word)
{
d.Values[i] += 1;
}
}
or
for (int i = 0; i < d.Count; i++)
{
if (d.ElementAt(i).Key == word)
{
var val = d.ElementAt(i).Value + 1;
d.RemoveAt(i);
d.Add(word, val);
}
}
Please modify this line and check if it works. it should.
Console.WriteLine("\t{0}:\t{1}", tempSortList.GetKey(i), tempSortList.GetByIndex(i));
to
var key = tempSortedList.Keys[i];
var value = tempSortedList.Values[i];
Console.WriteLine("\t{0}:\t{1}", key, value);
When trying to update a Dictionary with the following:
foreach(KeyValuePair<string, string> pair in dict)
{
dict[pair.Key] = "Hello";
}
And exception is thrown. Is there any way to dynamically update the dictionary WITHOUT making any kind of key or value backups?
EDIT!!!!!! View code. I realized that this portion was actually doable. The real case is this. I thought they would be the same, but they are not.
foreach(KeyValuePair<string, string> pair in dict)
{
dict[pair.Key] = pair.Key + dict[pair.Key];
}
Any reason why you're not iterating over the keys?
foreach(var key in dict.Keys)
{
dict[key] = "Hello";
}
You can either loop over the dictionary (you need to use ToList because you can't change a collection that is being looped over in a foreach loop)
foreach(var key in dict.Keys.ToList())
{
dict[key] = "Hello";
}
or you can do it in one line of LINQ as you're setting the same value to all the keys.
dict = dict.ToDictionary(x => x.Key, x => "Hello");
Updated question
foreach (var key in dict.Keys.ToList())
{
dict[key] = key + dict[key];
}
and the LINQ version
dict = dict.ToDictionary(x => x.Key, x => x.Key + x.Value);
If you want to avoid using ToList, you can use ElementAt so that you can modify the collection directly.
for (int i = 0; i < dict.Count; i++)
{
var item = dict.ElementAt(i);
dict[item.Key] = item.Key + item.Value;
}