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How do I parse "220510" so the value comes out as 22-05-10?

When I try this code:
string value = "220510"; // The `value` variable is always in this format
string key = "30";
string title;
switch (key)
{
case "30":
title = "Date: ";
Console.WriteLine($"{title} is {value}");
break;
}
the output looks like this:
My problem is that I don't know how to insert the '-' character to separate the month, day and year because I want it to display:
Date: is 22-05-10
Please show me how to parse it.

If you have a DateTime object:
oDate.toString("yy-MM-dd");
If you have a string you can either:
sDate = sDate.Insert(2,"-");
sDate = sDate.Insert(5,"-");
or go through DateTime again (for whatever reason):
string sDate = "220510";
CultureInfo provider = CultureInfo.InvariantCulture;
DateTime sDate = Convert.ParseExact(iDate, "yyMMdd", provider);
sDate.toString("yy-MM-dd");

Your question is: How do I parse the string 220510 date format so the value comes out as 22-05-10?
In this specific case, consider using the string.Substring method to pick out the digit pairs then use string interpolation to put them back together.
const string raw = "220510";
// To do a simple parse (not using a DateTime object)
var yearString = raw.Substring(0, 2);
var monthString = raw.Substring(2, 2);
var dayString = raw.Substring(4, 2);
var string_22_05_10 = $"{yearString}-{monthString}-{dayString}";
Console.WriteLine(string_22_05_10);

How do you convert date format to yyMMdd in cell click event?

var dateString1 = row.Cells["order_date"].Value.ToString();
txt_lot2.Text = row.Cells["lot_no"].Value.ToString() + " - " + dateString1;
This is string I am pulling from database on DataGridView. Right now it is in yy-MM-dd hh:mm:ss format. I want this value to be converted to yyMMdd when I click the cell. How do I convert this? Output should be something like:
lot_no - order date in yyMMdd
ex of original) K123-19-08-26 12:00:00 AM
ex of to be) K123 - 190826
Original database date format is yy-MM-dd hh:mm:ss and yes, I only want to convert to yyMMdd when I do a cell click event to fill up the textBox.

DateTime doesn't have a format of its own. You have to specify the format you want when using ToString().
var format = "yy-MM-dd hh:mm:ss";
var dateFromDB = "19-08-26 08:23:45";
DateTime.TryParseExact(
dateFromDB,
format,
System.Globalization.CultureInfo.InvariantCulture,
System.Globalization.DateTimeStyles.None,
out DateTime result);
Console.WriteLine(result.ToString("yyMMdd"));

No need to convert, just cut 8 chars and remove dashes:
var row = row.Cells["order_date"].Value.ToString(); // yy-mm-dd hh:mm:ss format
row = row.Substring(0, 8); // yy-mm-dd format
row = row.Replace("-", ""); // yymmdd format
row.Cells["order_date"] = row;

You need to handle three main events:
CellBeginEdit: here you will modify the format of the selected cell
CellParsing: here you will to all data conversion you need
CellEndEdit: here you enable the format back
Here a small working example of the code I've used, please note your code will be more complex because it will need to handle multiple columns and better formatting from the start, consider also I'm using edit mode with F2 to show the modified text:
private void DataGridView1_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e) =>
dataGridView1.CurrentCell.Style.Format = "yyMMdd";
private void DataGridView1_CellParsing(object sender, DataGridViewCellParsingEventArgs e)
{
DateTime.TryParseExact(dataGridView1.CurrentCell.EditedFormattedValue.ToString(), "yyMMdd", System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out DateTime dateToSaveInDb);
e.Value = dateToSaveInDb;
e.ParsingApplied = true;
dataGridView1.CurrentCell.Style.Format = "yy-MM-dd hh:mm:ss";
}
private void DataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e) =>
dataGridView1.CurrentCell.Style.Format = "yy-MM-dd hh:mm:ss";
I've tested this on a DataGridView populated like this
dataGridView1.DataSource = new List<Element> {
new Element{ EditableDate = DateTime.Now.AddDays(-1)},
new Element{ EditableDate = DateTime.Now},
new Element{ EditableDate = DateTime.Now.AddDays(1)}
}; ;
dataGridView1.EditMode = DataGridViewEditMode.EditOnF2;
Here the example class used
public class Element { public DateTime EditableDate { get; set; } }

Is there any way to format date cell in Excel with Invariant culture like in C#

The problem I am facing is that in a cell of an Excel sheet, a date is written. The cell is formatted with custom-format like:
[$-de]dd/mm/yyyy (dddd)
But only the (dddd) part is processed to give me "Sonntag" (Sunday in German language).
The datetime format is not fixed even though I have written the culture as "de" for the custom format. Is there any way to achieve the following result without altering the datetime format(yyyy-mm-dd)?
Tried Output Expected output
-------- ----------------------- -------------------
[$-fr]yyyy-mm-dd (dddd) => 2019-07-31 (dimanche) 31/7/2019 (dimanche)
[$-de]yyyy-mm-dd (dddd) => 2019-07-31 (Sonntag) 31.7.2019 (Sonntag)
[$-en]yyyy-mm-dd (dddd) => 2019-07-31 (Sunday) 7.31.2019 (Sunday)

Since you are specifying the exact data format in the string (the yyyy-mm-dd), excel will have to respect it when it opens. AFAIK, excel does not have a true "default" format that matches what you are looking for. If you open Excel and specify the format of a cell you can set the Culture/Country but you would still have to choose the format - the first one usually uses / as the separator.
But if you want to use what is in .NET, you could use CultureInfo.DateTimeFormat to get what I think you are after:
CultureInfo c;
var dt = new DateTime(2019,7,31);
c = new CultureInfo("fr-FR");
Console.WriteLine($"{c}: {c.DateTimeFormat.ShortDatePattern}");
Console.WriteLine(dt.ToString($"{c.DateTimeFormat.ShortDatePattern} (dddd)", c.DateTimeFormat));
Console.WriteLine();
c = new CultureInfo("de-DE");
Console.WriteLine($"{c}: {c.DateTimeFormat.ShortDatePattern}");
Console.WriteLine(dt.ToString($"{c.DateTimeFormat.ShortDatePattern} (dddd)", c.DateTimeFormat));
Console.WriteLine();
c = new CultureInfo("en-EN");
Console.WriteLine($"{c}: {c.DateTimeFormat.ShortDatePattern}");
Console.WriteLine(dt.ToString($"{c.DateTimeFormat.ShortDatePattern} (dddd)", c.DateTimeFormat));
Console.WriteLine();
Will give you this in the output:
fr-FR: dd/MM/yyyy
31/07/2019 (mercredi)
de-DE: dd.MM.yyyy
31.07.2019 (Mittwoch)
en-EN: M/d/yyyy
7/31/2019 (Wednesday)
To use in excel do this:
[TestMethod]
public void Culture_Info_Data_Format_Test()
{
//https://stackoverflow.com/questions/56985491/is-there-any-way-to-format-date-cell-in-excel-with-invariant-culture-like-in-c-s
var fileInfo = new FileInfo(#"c:\temp\Culture_Info_Data_Format_Test.xlsx");
if (fileInfo.Exists)
fileInfo.Delete();
using (var pck = new ExcelPackage(fileInfo))
{
var dt = new DateTime(2019, 7, 31);
var workbook = pck.Workbook;
var worksheet = workbook.Worksheets.Add("Sheet1");
worksheet.Column(1).Width = 50;
var c = new CultureInfo("fr-FR");
var format = $"[$-fr]{c.DateTimeFormat.ShortDatePattern} (dddd)";
worksheet.Cells[1, 1].Value = dt;
worksheet.Cells[1, 1].Style.Numberformat.Format = format;
c = new CultureInfo("de-DE");
format = $"[$-de]{c.DateTimeFormat.ShortDatePattern} (dddd)";
worksheet.Cells[2, 1].Value = dt;
worksheet.Cells[2, 1].Style.Numberformat.Format = format;
c = new CultureInfo("en-EN");
format = $"[$-en]{c.DateTimeFormat.ShortDatePattern} (dddd)";
worksheet.Cells[3, 1].Value = dt;
worksheet.Cells[3, 1].Style.Numberformat.Format = format;
pck.Save();
}
}
which gives this:

Try to use below formula in another column/cell, assuming you have a date starting from A1
=TEXT(A1,"mm/dd/yyy (dddd[$-fr])")
Hope it helps!
You can change the text string type from "/" to "." or whatever you want and the language format by changing this element [$-fr]

c# Help making values global

so I understand how to make global values and the fact that 1. you shouldn't do it and 2. you cannot use a value that was created in a different "context" however, I'm not sure how to correct this problem in my case. I think it will make sense if you read my code
//read in Load Query TestCSV
var sourcePath = #"D:\\Load Query test.csv"; //What is the inital CSV
var delimiter = ",";
var firstLineContainsHeaders = true; //CSV has headers
//creates temp file which takes less time than loading into memory
var tempPath = Path.Combine(#"D:", Path.GetRandomFileName());
var lineNumber = 0;
var splitExpression = new Regex(#"(" + delimiter + #")(?=(?:[^""]|""[^""]*"")*$)");
using (var writer = new StreamWriter(tempPath))
using (var reader = new StreamReader(sourcePath))
{
string line = null;
string[] headers = null;
if (firstLineContainsHeaders)
{
line = reader.ReadLine();
lineNumber++;
if (string.IsNullOrEmpty(line)) return; // file is empty;
headers = splitExpression.Split(line).Where(s => s != delimiter).ToArray();
writer.WriteLine(line); // write the original header to the temp file.
}
var i = 0; //used in 2nd while loop later
string lines = null;//used in next using statement
while ((line = reader.ReadLine()) != null)
{
lineNumber++;
var columns = splitExpression.Split(line).Where(s => s != delimiter).ToArray();
//make sure you always have the same number of columns in a line
if (headers == null) headers = new string[columns.Length];
if (columns.Length != headers.Length) throw new InvalidOperationException(string.Format("Line {0} is missing one or more columns.", lineNumber));
string badDate = "Date entered incorrectly"; //used in next while loop
// this while loop will read in the user input dateTime and use that to get the column from the PI server.
//if the date time is entered incorrectly it will tell the user to try to input the datetime again
while (i==0)
{
Console.WriteLine("Enter date, ex:16 Jun 8:30 AM 2008, Press enter when done"); //instruct the user in how to enter the date
string userInput = Console.ReadLine(); //read in the date the user enters
string format = "dd MMM h:mm tt yyyy"; //how the system will read the date entered
DateTime dateTime;
//if date is entered correctly, parse it, grab the parsed value dateTime and exit loop
if (DateTime.TryParseExact(userInput, format, CultureInfo.InvariantCulture, DateTimeStyles.None, out dateTime))
{
i = 1; //set the flag to exit while loop
}
//if input is bad return "Date entered incorrectly and run the loop again
else
{
Console.WriteLine(badDate);
i=0; //set the flag to run the loop again
}
}
var del = ","; //used in next using statement
var SplitExpression = new Regex(#"(" + del + #")(?=(?:[^""]|""[^""]*"")*$)"); //used in next using statement
//Use the dateTime from the previous while loop and use it to add each point in "testpts.csv" to "Load Query Test.csv"
using (StreamReader tags = new StreamReader(#"D:\\testpts.csv"))
{
// string userInput = Console.ReadLine();
string format = "dd MMM h:mm tt yyyy";
DateTime.TryParseExact(userInput, format, CultureInfo.InvariantCulture, DateTimeStyles.None, out dateTime);
lines = tags.ReadLine();
var columns1 = SplitExpression.Split(lines).Where(s => s != del).ToArray();
var point = PIPoint.FindPIPoint(piServer, lines);
var value = point.RecordedValue(dateTime);
string returnXml = string.Format(#"<value=""{0}"" />", value);
columns[15] = columns[15].Replace("0", returnXml); //column the point should be placed in (in Load Query Test.csv)
}
//if statement that will replace any extra 0 testpt values with column 13 values
if (columns[15].Contains("0"))
{
columns[15] = columns[15].Replace("0", columns[13]);
}
writer.WriteLine(string.Join(delimiter, columns));
}
}
File.Delete(sourcePath); //delete the original csv
File.Move(tempPath, sourcePath); //replace the old csv with edited one
Console.ReadLine();
I'm getting the error in the using statement:
using (StreamReader tags = new StreamReader(#"D:\\testpts.csv"))
{
// string userInput = Console.ReadLine();
string format = "dd MMM h:mm tt yyyy";
DateTime.TryParseExact(userInput, format, CultureInfo.InvariantCulture, DateTimeStyles.None, out dateTime);
lines = tags.ReadLine();
var columns1 = SplitExpression.Split(lines).Where(s => s != del).ToArray();
var point = PIPoint.FindPIPoint(piServer, lines);
var value = point.RecordedValue(dateTime);
string returnXml = string.Format(#"<value=""{0}"" />", value);
columns[15] = columns[15].Replace("0", returnXml); //column the point should be placed in (in Load Query Test.csv)
}
In this case the dateTime and userInput values are obviously out of context. I need them created in the previous while loop however because I want the user to be able to enter the correct date only once and ensure that it is entered correctly to make sure the script will actually pull data.
Please let me know if there is another way I can order my code or how I can make userInput and dateTime global. Thank you

Your problem lies in the "dateTime" variable. "userInput" is fine, the inner using statement has access to the scope of its outer using statement, because the inner one is part of the outer's scope.
The problem is with "dateTime" - the variable is declared inside a while loop, and there is a using block afterwards - after the variable is not available anymore, because the scope was disposed - which references a non existent variable.
Solution: move the declaration of your dateTime variable out of the while. Say, a line before the while's definition.

Without critisizing your code to much ... here an answer. You should be able to walk yourself from here on
Split the declaration of the variable with it's assignment
string userInput = Console.ReadLine();
to
string userInput;
userInput = Console.ReadLine();
Move the declarations (the first line) outside of the outer Loop.
Edit: Please, also have a look at Properties (you may call them
globals)

Chart shows wrong dates at X axis

I am reading date/time and data from a csv file and store this in a line chart. My date/time string is 1-1-2014 21:55:42 or 18-02-2014 00:00:00 which is actually the first entry and i have for a couple of hours data.
First i'm setting the chartArea X axis lablestyle to the proper format: "d-M-yyyy HH:mm:ss".
Then i parse my actual date string to a DateTime format using the same format as above: d-M-yyyy HH:mm:ss. And add the data to the chart.
I ensure you my date is correct:
And my code:
private void button2_Click_1(object sender, EventArgs e)
{
string line;
char[] delimiters = { ';', ',', '|' };
chart1.Series["Series1"].XValueType = ChartValueType.Time;
chart1.ChartAreas["ChartArea1"].AxisX.LabelStyle.Format = "d-M-yyyy HH:mm:ss";
chart1.Series["Series1"].Points.Clear();
using (System.IO.StreamReader sr = new System.IO.StreamReader(filename))
{
while (!sr.EndOfStream)
{
line = sr.ReadLine();
DateTime newDateTime = new DateTime();
string[] part = line.Split(delimiters);
Console.WriteLine(part[0]);
newDateTime = DateTime.ParseExact(
part[0],
"d-M-yyyy HH:mm:ss",
CultureInfo.InvariantCulture
);
chart1.Series["Series1"].Points.AddXY(newDateTime, part[5]);
}
}
chart1.Refresh();
}

Problem : You have set the Custom Format for X-Axis as d-M-yyyy HH:mm:ss but you are just providing the datetime without formatting it.
Replace This:
chart1.Series["Series1"].Points.AddXY(newDateTime, part[5]);
With This:
chart1.Series["Series1"].Points.AddXY(
newDateTime.ToString("d-M-yyyy HH:mm:ss"), part[5]);