Develop Reference

Efficient way to concatenate strings using c# [duplicate]

This question already has answers here:
Most efficient way to concatenate strings?
(18 answers)
Closed last month.
I have following code snippet that will append filename with current timestamp and it's working fine.
Just want to make sure this is best way to append strings in c# 10, if not then how we can we make below code more efficient?
ex: testfile.txt ->o/p testfile_timestamp.txt
string[] strName = formFile.FileName.Split('.');
string updatedFilename = strName[0] + "_"
+ DateTime.Now.ToUniversalTime().ToString("THHmmssfff") + "." +
strName[strName.Length - 1];

How about this:
// Just a stupid method name for demo, you'll find a better one :)
public static string DatifyFileName(string fileName)
{
// Use well tested Framework method to get filename without extension
var nameWithoutExtension = System.IO.Path.GetFileNameWithoutExtension(fileName);
// Use well tested Framework method to get extension
var extension = System.IO.Path.GetExtension(fileName);
// interpolate to get the desired output.
return $"{nameWithoutExtension}_{DateTime.Now.ToUniversalTime().ToString("THHmmssfff")}{extension}";
}
Or if you are familiar with Span<char>:
public static string DatifyFileName(ReadOnlySpan<char> fileName)
{
var lastDotIndex = fileName.LastIndexOf('.');
//Maybe : if( lastDotIndex < 0 ) throw ArgumentException("no extension found");
var nameWithoutExtension = fileName[..lastDotIndex];
var extension = fileName[lastDotIndex..];
return $"{nameWithoutExtension}_{DateTime.Now.ToUniversalTime().ToString("THHmmssfff")}{extension}";
}
Fiddle
And just to give some fire to the discussion :D ...
BenchmarkDotNet=v0.13.3, OS=Windows 10 (10.0.19044.2364/21H2/November2021Update)
Intel Core i9-10885H CPU 2.40GHz, 1 CPU, 16 logical and 8 physical cores
.NET SDK=7.0.101
[Host] : .NET 7.0.1 (7.0.122.56804), X64 RyuJIT AVX2
DefaultJob : .NET 7.0.1 (7.0.122.56804), X64 RyuJIT AVX2
| Method | Mean | Error | StdDev | Ratio | RatioSD | Gen0 | Allocated | Alloc Ratio |
|----------------- |-----------:|---------:|---------:|------:|--------:|-------:|----------:|------------:|
| Interpolated | 906.7 ns | 16.92 ns | 16.61 ns | 1.08 | 0.02 | 0.0458 | 384 B | 1.66 |
| InterpolatedSpan | 842.0 ns | 13.06 ns | 12.22 ns | 1.00 | 0.00 | 0.0277 | 232 B | 1.00 |
| StringBuilder | 1,010.8 ns | 6.70 ns | 5.94 ns | 1.20 | 0.02 | 0.1068 | 904 B | 3.90 |
| Original | 960.0 ns | 18.68 ns | 19.19 ns | 1.14 | 0.03 | 0.0734 | 616 B | 2.66 |
// * Hints *
Outliers
Benchmark.StringBuilder: Default -> 1 outlier was removed (1.03 us)
Benchmark.Original: Default -> 2 outliers were removed (1.03 us, 1.06 us)
// * Legends *
Mean : Arithmetic mean of all measurements
Error : Half of 99.9% confidence interval
StdDev : Standard deviation of all measurements
Ratio : Mean of the ratio distribution ([Current]/[Baseline])
RatioSD : Standard deviation of the ratio distribution ([Current]/[Baseline])
Gen0 : GC Generation 0 collects per 1000 operations
Allocated : Allocated memory per single operation (managed only, inclusive, 1KB = 1024B)
Alloc Ratio : Allocated memory ratio distribution ([Current]/[Baseline])
1 ns : 1 Nanosecond (0.000000001 sec)

Strings are immutable. whenever you modify any string, it is recreated in the memory. Hence to overcome this you should always use StringBuilder. Sample code shown below:
string[] strName = formFile.FileName.Split('.');
StringBuilder updatedFilename = new StringBuilder();
updatedFilename.Append(strName[0]);
updatedFilename.Append("_");
updatedFilename.Append(DateTime.Now.ToUniversalTime().ToString("THHmmssfff"));
updatedFilename.Append(".");
updatedFilename.Append(strName[strName.Length - 1]);
// You can get this using `ToString()` method
string filename = updatedFilename.ToString();

UnionBy() EF Core

I have this ef query that give me the following result
IQueryable<A>
| Id | count |
| 1 | 5 |
| 2 | 6 |
IQueryable<B>
| Id | count |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
When I do
IQueryable<Something> C = A.union(B)
Result that I got is this
| Id | count |
| 1 | 5 |
| 2 | 6 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
Whish is logical.
What I want is a UnionBy(Id)
IQueryable<Something> C = A.unionBy(B,c=>c.Id)
and this work perfectly in my case
| Id | count |
| 1 | 5 | -- FROM A
| 2 | 6 | -- FROM A
| 3 | 9 | -- FROM B
If the Query A or B are already executed by that I mean a ToList() was made it work perfectly and I have no problem in anyway.
But in my case, both queries are not executed and thus using this function result in.
System.InvalidOperationException query could not be translated.
the alternative is to use a GroupBy however I have no idea how to replacte UnionBy behavior with the GroupBy
FYI: the query works perfectly using the IQueryable.Union
and it's mandatory in my case that the request stay in IQueryable and not executed until later
UPDATE
⚠️ The solution that I'm looking for must stay in IQueryable without a toList() execution

"query could not be translated" usually means that EF doesn't support a certain LINQ or language construct as it can't translate it into SQL. One way to make this work is to force the evaluation of the expression client-side by adding e.g. ToList() or likes on the query parts before executing the UnionBy:
IQueryable<Something> C = A.ToList().UnionBy(B.ToList(),c=>c.Id);

The solution is simple you filtre A From B using the following
IQueryable<Something> C = A.Union(B.where(b=> A.All(a=>a.Id != b.Id))

How does Apache Ignite supports partitioning?

I am trying to experiment with data partition in Apache Ignite using .NET thin client.
In article https://apacheignite.readme.io/docs/cache-modes it's written that in partition mode "the overall data set is divided equally into partitions and all partitions are split equally between participating nodes". So I am expecting cache with 1000 records to be splitted beetween 3 Ignite nodes equally: 333(4) on each node. But when I start 3 instances of Ignite on local machine (using platforms\dotnet\bin\Apache.Ignite.exe) I can see only that 1000 records are replicated on all nodes: 1000 same records on each node. I tried to disable backups creation: 1000 records were created only on first node. Currently I use sequental Int32 values as cache key. But even when I ran LinqExample with colocated employes (with AffinityKey) data was't splitted beetween nodes.
I also tried to experiment with cache configuration:
var cacheConfiguration = new CacheClientConfiguration(_key, cacheEntity);
cacheConfiguration.CacheMode = CacheMode.Partitioned;
cacheConfiguration.Backups = 0;
cacheConfiguration.ReadFromBackup = false;
cacheConfiguration.RebalanceMode = CacheRebalanceMode.Sync;
cacheConfiguration.RebalanceOrder = 1;
cacheConfiguration.RebalanceThrottle = TimeSpan.FromSeconds(1);
cacheConfiguration.RebalanceDelay = TimeSpan.Zero;
cacheConfiguration.RebalanceBatchSize = 1024;
var cache = _igniteClient.CreateCache<int, TEntityType>(cacheConfiguration).WithExpiryPolicy(_expiryPolicy);
Perhaps I don't understand the main concept of data partitioning implemented in Apache Ignite or Apache.Ignite.exe needs some additional configuration to support data partitioning. Execuse me if it's a simple question.
PS. I am using DBeaver to check amount of records on each node. 3 ignite instances by default uses ports 10800, 10801, 10802 for .NET client requests. So I am using localhost:10800, localhost:10801, localhost:10802 adresses in DBeaver.

To get the number of entries per node, use included Visor tool.
Go to Ignite bin directory
Start ignitevisorcmd
Use open to connect to a cluster
Type cache -a
Generated report will include table with node specifics:
Nodes for: person-cache-1(#c0)
+====================================================================================================================+
| Node ID8(#), IP | CPUs | Heap Used | CPU Load | Up Time | Size (Primary / Backup) | Hi/Mi/Rd/Wr |
+====================================================================================================================+
| 1F81F615(#n0), 127.0.0.1 | 12 | 10.26 % | 0.00 % | 00:08:15.394 | Total: 513 (513 / 0) | Hi: 0 |
| | | | | | Heap: 0 (0 / <n/a>) | Mi: 0 |
| | | | | | Off-Heap: 513 (513 / 0) | Rd: 0 |
| | | | | | Off-Heap Memory: <n/a> | Wr: 0 |
+-----------------------------+------+-----------+----------+--------------+---------------------------+-------------+
| FBCF3B0F(#n1), 127.0.0.1 | 12 | 15.23 % | 0.00 % | 00:07:46.647 | Total: 486 (486 / 0) | Hi: 0 |
| | | | | | Heap: 0 (0 / <n/a>) | Mi: 0 |
| | | | | | Off-Heap: 486 (486 / 0) | Rd: 0 |
| | | | | | Off-Heap Memory: <n/a> | Wr: 0 |
+--------------------------------------------------------------------------------------------------------------------+
According to Size(Primary/...) 999 entries are split between two nodes, with 513 entries on the first node and 486 on the second node.
Check "Primary" and not "Total"; "Total" is sum of primary entries and replicated entries from other nodes. Shown setup does not have replication, so it is equal to "Primary".
If a cluster had three nodes, and a cache had 2 replicas (so 3 copies in total), then the "Total" number on one node will be close to a total number of entries (as each node contains all entries, either as a primary node or backup node for two other nodes), "Primary" would be approximately 1/3 of the total and "Backup" would be 2/3.

Trim string in c# output last string

I'm currently making a Game and I have already split the string everything right but how I can trim the string and output the last line or a line in the middle?
Code:
text = "Username:King100 ID:100 Level:10";
string[] splittext = text.Split(' ');
foreach (var texs in splittext)
{
Console.WriteLine(texs);
}
Output:
Username:King100
ID:100
Level:10
I just want display the level 10 in the Console how thats works?
thanxs for helping.
Edit: the level can be changed often like 10 or 100 or 1000

Regex is more flexible solution. But if your text format is contsant, you can use this simple way:
string level = text.Substring(text.LastIndexOf(':') + 1);

You can also use a Regular Expression to solve this:
var regex = new Regex(#"Level:(?<Level>\d*)");
var matches = regex.Matches("Username:King100 ID:100 Level:10");
if (matches.Count > 0 && matches[0].Success)
{
Console.WriteLine(matches[0].Groups["Level"].Value);
}

var text = "Username:King100 ID:100 Level:10";
/*
Splits the given string on spaces and then splits on ":"
and creates a Dictionary ("Dictionary<TKey, TValue>")
*/
var dict = text.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
.Select(part => part.Split(':'))
.ToDictionary(split => split[0], split => split[1]);
//If the dictionary count is greater than Zero
if(dict.Count > 0)
{
var levelValue = dict["Level"].ToString();
}

OK, because i'm annoying and totally bored of work, i decided to benchmark everyone's solutions.
The premise was simply to make an array of 1000 (scale) lines of strings (in the given format) with random positive int on the end;
Note : I made every solution int.Parse the result, as it seemed more useful
Mine
This just uses fixed, unsafe, pointers and no error checking
var level = 0;
fixed (char* pitem = item)
{
var len = pitem + item.Length;
for (var p = pitem ; p < len; p++)
if (*p >= '0' && *p <= '9')
level = level * 10 + *p - 48;
else
level = 0;
}
Results
Mode : Release
Test Framework : .NET Framework 4.7.1
Benchmarks runs : 1000 times (averaged)
Scale : 1,000
Name | Average | Fastest | StDv | Cycles | Pass | Gain
--------------------------------------------------------------------------
Mine | 0.095 ms | 0.085 ms | 0.01 | 317,205 | Yes | 96.59 %
Sanan | 0.202 ms | 0.184 ms | 0.02 | 680,747 | Yes | 92.75 %
Zaza | 0.373 ms | 0.316 ms | 0.10 | 1,254,302 | Yes | 86.60 %
Kishore | 0.479 ms | 0.423 ms | 0.06 | 1,620,756 | Yes | 82.81 %
Hussein | 1.045 ms | 0.946 ms | 0.11 | 3,547,305 | Yes | 62.50 %
Maccettura | 2.787 ms | 2.476 ms | 0.39 | 9,474,133 | Base | 0.00 %
Hardkoded | 6.691 ms | 5.927 ms | 0.67 | 22,750,311 | Yes | -140.09 %
Tom | 11.561 ms | 10.635 ms | 0.78 | 39,344,419 | Yes | -314.80 %
Summary
All the solutions do different things in different ways, comparing them is not really apples to apples.
Don't use mine, its totally unrealistic and only for fun. Use the version that makes the most sense to you, that is the most robust and easiest to maintain.
As always, regex is the slowest.

If level is always the last part of the string, and all you care about is the actual number, then you can just do:
var level = text.Split(':').LastOrDefault();
This would just split on ':' and give you the last (or default) element. Given your example input, level = "10".

Try this:
string input = "Username:King100 ID:100 Level:10";
Match m = Regex.Match(input, #"\s*Level:(?<level>\d+)");
if (m.Success&& m.Groups["level"].Success)
Console.WriteLine(m.Groups["level"].Value);
Also works for:
string input = "Username:King100 Level:10 ID:100";

string text = texs.Substring(texs.IndexOf("Level:")+6);
System.Console.WriteLine(text);

Aligning multiple line strings c# console app

I'm making a blackjack game and would like to show the cards next to each other as the player draws them. I have the cards saved as strings within a card object and the strings look sort of like this I couldn't figure out how to actually put it in here:
public void CreateDeck()
{
myDeck[0] = new Card(1, "hearts", #"
______________
| A |
| |
| |
| |
| HEARTS |
| |
| |
| A |
|______________|", #"
______________
|//////////////|
|//////////////|
|//////////////|
|//////////////|
|//////////////|
|//////////////|
|//////////////|
|//////////////|
|//////////////|");
The ace of hearts is basically what I would like to output. I can output the cards but every time I output a second card it goes to a new line instead of next to the first card
I would like the output to look like this to display a players and dealers hand
______________ ______________
| J | | 10 |
| | | |
| | | |
| | | |
| CLUBS | | HEARTS |
| | | |
| | | |
| J | | 10 |
|______________| |______________|

You could try redrawing the whole set of cards as they are drawn. Keep the cards in a collection (let's say Cards) with a method to output the art (overriding the public ToString here) Then you will need to split by the carriage return and draw line by line as below. As others have suggested, you will find it much easier (less hacky) to do this in a Windows app.
var cardLines = cards.Select(x =>
x.ToString().Split('\r').ToList().Select(y => y.Replace("\r", string.Empty).Replace("\n", string.Empty)
).ToList()).ToList();
var maximumCardHeight = cardLines.Max(x => x.Count);
for (var i = 0; i < maximumCardHeight - 1; i++)
{
cardLines.ForEach(x =>
{
if (i < x.Count)
Console.Write(x[i]);
});
Console.WriteLine();
}