I have this enumeration:
public enum SymbolPair
{
AUDJPY = 0, AUDNZD, AUDUSD, CADJPY, CHFJPY, EURCHF, EURGBP, EURJPY, EURUSD, GBPJPY, GBPUSD, NZDUSD, USDCAD, USDCHF, USDJPY
}
And I have a collection of symbol strings
List<string> symbols = new List<string>(){ };
Symbols are loaded into the collection dynamically depending on which symbols are entered in the input parameters. They can be loaded in any order and any count.
So for example one set can load in "EUR/USD", "CHFJPY", "GBPUSD"
I need to find the indexes corresponding to the index of the enumeration type. For example in this case I need the indexes 8, 4, and 10.
Can someone please give an idea how to do this with linq or delegates or any other efficient way.
Thanks
EDIT: I need something along these lines but this doesn't work since linq does return a single value. How can I get that single index?
SymbolPair[] enumList = (SymbolPair[])Enum.GetValues(typeof(SymbolPair));
foreach (string symbol in symbols)
{
int instrumentIndex = from symbolPair in enumList
where symbolPair.ToString() == symbol
select (int)symbolPair;
}
Ok i got it. Thanks anyways.
SymbolPair[] symbolEnumList = (SymbolPair[])Enum.GetValues(typeof(SymbolPair));
int instrumentIndex = (int)symbolEnumList.Single(symbolPair => symbolPair.ToString() == instr.Symbol.ToString());
Related
In C# .NET 4.0, I am struggling to come up with the most efficient way to determine if the contents of 2 lists of items contain any differences.
I don't need to know what the differences are, just true/false whether the lists are different based on my criteria.
The 2 lists I am trying to compare contain FileInfo objects, and I want to compare only the FileInfo.Name and FileInfo.LastWriteTimeUtc properties of each item. All the FileInfo items are for files located in the same directory, so the FileInfo.Name values will be unique.
To summarize, I am looking for a single Boolean result for the following criteria:
Does ListA contain any items with FileInfo.Name not in ListB?
Does ListB contain any items with FileInfo.Name not in ListA?
For items with the same FileInfo.Name in both lists, are the FileInfo.LastWriteTimeUtc values different?
Thank you,
Kyle
I would use a custom IEqualityComparer<FileInfo> for this task:
public class FileNameAndLastWriteTimeUtcComparer : IEqualityComparer<FileInfo>
{
public bool Equals(FileInfo x, FileInfo y)
{
if(Object.ReferenceEquals(x, y)) return true;
if (x == null || y == null) return false;
return x.FullName.Equals(y.FullName) && x.LastWriteTimeUtc.Equals(y.LastWriteTimeUtc);
}
public int GetHashCode(FileInfo fi)
{
unchecked // Overflow is fine, just wrap
{
int hash = 17;
hash = hash * 23 + fi.FullName.GetHashCode();
hash = hash * 23 + fi.LastWriteTimeUtc.GetHashCode();
return hash;
}
}
}
Now you can use a HashSet<FileInfo> with this comparer and HashSet<T>.SetEquals:
var comparer = new FileNameAndLastWriteTimeUtcComparer();
var uniqueFiles1 = new HashSet<FileInfo>(list1, comparer);
bool anyDifferences = !uniqueFiles1.SetEquals(list2);
Note that i've used FileInfo.FullName instead of Name since names aren't unqiue at all.
Sidenote: another advantage is that you can use this comparer for many LINQ methods like GroupBy, Except, Intersect or Distinct.
This is not the most efficient way (probably ranks a 4 out of 5 in the quick-and-dirty category):
var comparableListA = ListA.Select(a =>
new { Name = a.Name, LastWrite = a.LastWriteTimeUtc, Object = a});
var comparableListB = ListB.Select(b =>
new { Name = b.Name, LastWrite = b.LastWriteTimeUtc, Object = b});
var diffList = comparableListA.Except(comparableListB);
var youHaveDiff = diffList.Any();
Explanation:
Anonymous classes are compared by property values, which is what you're looking to do, which led to my thinking of doing a LINQ projection along those lines.
P.S.
You should double check the syntax, I just rattled this off without the compiler.
I am trying to select some records using LINQ for Entities (EF4 Code First).
I have a table called Monitoring with a field called AnimalType which has values such as
"Lion,Tiger,Goat"
"Snake,Lion,Horse"
"Rattlesnake"
"Mountain Lion"
I want to pass in some values in a string array (animalValues) and have the rows returned from the Monitorings table where one or more values in the field AnimalType match the one or more values from the animalValues. The following code ALMOST works as I wanted but I've discovered a major flaw with the approach I've taken.
public IQueryable<Monitoring> GetMonitoringList(string[] animalValues)
{
var result = from m in db.Monitorings
where animalValues.Any(c => m.AnimalType.Contains(c))
select m;
return result;
}
To explain the problem, if I pass in animalValues = { "Lion", "Tiger" } I find that three rows are selected due to the fact that the 4th record "Mountain Lion" contains the word "Lion" which it regards as a match.
This isn't what I wanted to happen. I need "Lion" to only match "Lion" and not "Mountain Lion".
Another example is if I pass in "Snake" I get rows which include "Rattlesnake". I'm hoping somebody has a better bit of LINQ code that will allow for matches that match the exact comma delimited value and not just a part of it as in "Snake" matching "Rattlesnake".
This is a kind of hack that will do the work:
public IQueryable<Monitoring> GetMonitoringList(string[] animalValues)
{
var values = animalValues.Select(x => "," + x + ",");
var result = from m in db.Monitorings
where values.Any(c => ("," + m.AnimalType + ",").Contains(c))
select m;
return result;
}
This way, you will have
",Lion,Tiger,Goat,"
",Snake,Lion,Horse,"
",Rattlesnake,"
",Mountain Lion,"
And check for ",Lion," and "Mountain Lion" won't match.
It's dirty, I know.
Because the data in your field is comma delimited you really need to break those entries up individually. Since SQL doesn't really support a way to split strings, the option that I've come up with is to execute two queries.
The first query uses the code you started with to at least get you in the ballpark and minimize the amount of data you're retrieving. It converts it to a List<> to actually execute the query and bring the results into memory which will allow access to more extension methods like Split().
The second query uses the subset of data in memory and joins it with your database table to then pull out the exact matches:
public IQueryable<Monitoring> GetMonitoringList(string[] animalValues)
{
// execute a query that is greedy in its matches, but at least
// it's still only a subset of data. The ToList()
// brings the data into memory, so to speak
var subsetData = (from m in db.Monitorings
where animalValues.Any(c => m.AnimalType.Contains(c))
select m).ToList();
// given that subset of data in the List<>, join it against the DB again
// and get the exact matches this time
var result = from data in subsetData
join m in db.Monitorings on data.ID equals m.ID
where data.AnimalType.Split(',').Intersect(animalValues).Any ()
select m;
return result;
}
I have the following snippet that I currently use to run a .Contains() with a list of Ids passed as a comma separated list from users. This code works perfectly and the data is filtered exactly as I want it to be:
// Handle id in() statements explicitly, dynamic expression can't parse them
var idIn = new Regex("id in ?(.*)", RegexOptions.IgnoreCase);
if (idIn.IsMatch(predicate))
{
Match list = new Regex(#"in ?\((.*)\)", RegexOptions.IgnoreCase).Match(predicate);
string ins = list.Groups[1].ToString();
// Split ins and store as List<>
List<int> splitValues = ins.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries).Select(i => Convert.ToInt32(i)).ToList();
return source.Where(u => splitValues.Contains(u.Id));
}
I want to be able to use this same idea, except with ANY property of the u object using reflection. I had a version of this working at some point, but cannot for the life of me figure out what has changed or why it stopped working. Here is the version I have that I cannot get working again:
Match splitIn = new Regex(#"([a-zA-Z0-9\.]*) IN ?\((.*)\)", RegexOptions.IgnoreCase).Match(predicate);
string property = splitIn.Groups[1].ToString();
string ins = splitIn.Groups[2].ToString().Trim(new[] {'\'', '"'}); // Trim off separator quotes
List<string> splitValues = ins.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries).ToList();
for (int i = 0; i < splitValues.Count; i++)
{
splitValues[i] = splitValues[i].Trim(new[] {'\'', '"'});
}
Expression<Func<U, bool>> contains = u => ListContainsProperty(u, splitValues, property);
return source.Where(contains);
private static bool ListContainsProperty<U>(U u, ICollection<string> list, string property)
{
string[] split = property.Split(new[] {"."}, StringSplitOptions.RemoveEmptyEntries);
object value = split.Aggregate<string, object>(u, (current, prop) => current.GetType().GetProperty(prop).GetValue(current, null));
return list.Contains(value.ToString());
}
As I said I once had SOME version of this working, but cannot figure out what has changed. Is there something blatantly obvious that I am missing that would help me get this functional again?
Edit: As far as I can tell the ListContainsProperty method is never actually running. Adding a "throw new Exception()" does nothing. I just get the full unfiltered list back.
I think the underlying problem is using "Expression"
you need to compile an Expression.
For example in your code
Expression<Func<U, bool>> contains = u => ListContainsProperty(u, splitValues, property);
is data and not a function. In order to use it you need to compile it.
Func<U, bool> compiled = contains.Compile();
"compiled" variable will call the "ListContainsProperty" method.
I have a program with multiple int variables where individual counts are added to the specific variable each time a set fail condition is encountered. I want the user to be able to track how many failures of each category they have encountered by a button click. I want to display the range on a datagridview in order from highest value integer down to lowest. I also need to display in the adjacent column the name of the test step that relates to the value. My plan was to use Array.sort to order the integers but i then lose track of their names so cant assign the adjacent string column. I tried using a hashtable but if i use the string as a key it sorts alphabetically not numerically and if i use the integer as a key i get duplicate entries which dont get added to the hash table. here is some of the examples i tried but they have the aforementioned problems. essentially i want to end with two arrays where the order matches the naming and value convention. FYI the variables were declared before this section of code, variables ending in x are the string name for the (non x) value of the integer.
Hashtable sorter = new Hashtable();
sorter[download] = downloadx;
sorter[power] = powerx;
sorter[phase] = phasex;
sorter[eeprom] = eepromx;
sorter[upulse] = upulsex;
sorter[vpulse] = vpulsex;
sorter[wpulse] = wpulsex;
sorter[volts] = voltsx;
sorter[current] = currentx;
sorter[ad] = adx;
sorter[comms] = commsx;
sorter[ntc] = ntcx;
sorter[prt] = prtx;
string list = "";
string[] names = new string[13];
foreach (DictionaryEntry child in sorter)
{
list += child.Value.ToString() + "z";
}
int[] ordered = new int[] { download, power, phase, eeprom, upulse, vpulse, wpulse, volts, current, ad, comms, ntc, prt };
Array.Sort(ordered);
Array.Reverse(ordered);
for (int i = 0; i < sorter.Count; i++)
{
int pos = list.IndexOf("z");
names[i] = list.Substring(0, pos);
list = list.Substring(pos + 1);
}
First question here so hope its not too longwinded.
Thanks
Use a Dictionary. And you can order it by the value : myDico.OrderBy(x => x.Value).Reverse(), the sort will be numerical descending. You just have to enumerate the result.
I hope I understand your need. Otherwise ignore me.
You want to be using a
Dictionary <string, int>
to store your numbers.I'm not clear on how you're displaying results at the end - do you have a grid or a list control?
You ask about usings. Which ones do you already have?
EDIT for .NET 2.0
There might be a more elegant solution, but you could implement the logic by putting your rows in a DataTable. Then you can make a DataView of that table and sort by whichever column you like, ascending or descending.
See http://msdn.microsoft.com/en-us/library/system.data.dataview(v=VS.80).aspx for example.
EDIT for .NET 3.5 and higher
As far as sorting a Dictionary by its values:
var sortedEntries = myDictionary.OrderBy(pair => pair.Value);
If you need the results to be a Dictionary, you can call .ToDictionary() on that. For reverse order, use .OrderByDescending(pair => pair.Value).
I am attempting to get unique values in a list of similar value distinguished only by a one element in a pipe delimited string... I keep getting at least one object must implement Icomparable. I don't understand why I keep getting that. I am able to groupBy that value... Why can't I find the max... I guess it is looking for something to compare it with. If I get the integer version will it stop yelling at me? This is the last time I am going to try using LINQ...
var queryResults = PatientList.GroupBy(x => x.Value.Split('|')[1]).Select(x => x.Max());
I know I can get the unique values some other way. I am just having a hard time figuring it out. In that List I know that the string with the highest value amongst its similar brethren is the one that I want to add to the list. How can I do that? I am totally drawing a blank because I have been trying to get this to work in linq for the last few days with no luck...
foreach (XmlNode node in nodeList)
{
XmlDocument xDoc = new XmlDocument();
xDoc.LoadXml(node.OuterXml);
string popPatInfo = xDoc.SelectSingleNode("./template/elements/element[#name=\"FirstName\"]").Attributes["value"].Value + ", " + xDoc.SelectSingleNode("./template/elements/element[#name=\"LastName\"]").Attributes["value"].Value + " | " + DateTime.Parse(xDoc.SelectSingleNode("./template/elements/element[#name=\"DateOfBirth\"]").Attributes["value"].Value.Split('T')[0]).ToString("dd-MMM-yyyy");
string patientInfo = xDoc.SelectSingleNode("./template/elements/element[#name=\"PatientId\"]").Attributes["value"].Value + "|" + xDoc.SelectSingleNode("./template/elements/element[#name=\"PopulationPatientID\"]").Attributes["enc"].Value;// +"|" + xDoc.SelectSingleNode("./template/elements/element[#name=\"AdminDate\"]").Attributes["value"].Value;
int enc = Int32.Parse(patientInfo.Split('|')[1]);
if (enc > temp)
{
lastEncounter.Add(enc, patientInfo);
temp = enc;
}
//lastEncounter.Add(Int32.Parse(patientInfo.Split('|')[1]));
PatientList.Add( new SelectListItem { Text = popPatInfo, Value = patientInfo });
}
I was thinking about using some kind of temp variable to find out what is the highest value and then add that string to the List. I am totally drawing a blank however...
Here I get the IDs in an anonymous type to make it readable.
var patientEncounters= from patient in PatientList
let PatientID=Int32.Parse(patient.Value.Split('|')[0])
let EncounterID=Int32.Parse(patient.Value.Split('|')[1])
select new { PatientID, EncounterID };
Then we group by UserID and get the last encounter
var lastEncounterForEachUser=from pe in patientEncounters
group pe by pe.PatientID into grouped
select new
{
PatientID=grouped.Key,
LastEncounterID=grouped.Max(g=>g.EncounterID)
};
Linq doesn't know how to compare 2 Patient objects, so it can't determine which one is the "greatest". You need to make the Patient class implement IComparable<Patient>, to define how Patient objects are compared.
// Compare objets by Id value
public int CompareTo(Patient other)
{
return this.Id.CompareTo(other.Id);
}
Another option is to use the MaxBy extension method available in Jon Skeet's MoreLinq project:
var queryResults = PatientList.GroupBy(x => x.Value.Split('|')[1])
.Select(x => x.MaxBy(p => p.Id));
EDIT: I assumed there was a Patient class, but reading your code again, I realize it's not the case. PatientList is actually a collection of SelectListItem, so you need to implement IComparable in that class.