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Delete character out of string

I am having some problems with a quite easy task - i feel like im missing something very obvious here.
I have a .csv file which is semicolon seperated. In this file are several numbers that contain dots like "1.300" but there are also dates included like "2015.12.01". The task is to find and delete all dots but only those that are in numbers and not in dates. The dates and numbers are completely variable and never at the same position in the file.
My question now: What is the 'best' way to handle this problem?
From a programmers point of view: Is it a good solution to just split at every semilicon, count the dots and if there is only one dot, delete it? This is the only way to solve the problem i could think of by now.
Example source file:
2015.12.01;
13.100;
500;
1.200;
100;
Example result:
2015.12.01;
13100;
500;
1200;
100;

If you can rely on the fact that dates have two dots and numbers just one, you can use that as a filter:
string s = "123.45";
if (s.Count(x => x == '.') == 1)
{
s = s.Replace(".", null);
}

The source file looks like a valid file generated by a program running on a machine whose locale uses . as the thousand separator (most of Europe does) and date separator (German locales only I think). Such locales also use ; as the list separator.
If the question was only how to parse such dates, numbers, the answer would be to pass the proper culture to the parse function, eg: decimal.Parse("13.500",new CultureInfo("de-at")) would return 13500. The actual issue though is that the data must be fed to another program that uses . as the decimal separator.
The safest option would be to change the locale used by the exporting program, eg change the thread CultureInfo if the exporter is a .NET program, the locale in an SSIS package etc, to a locale like en-gb to export with . and avoid the weird date format. This assumes that the next program in the pipeline doesn't use German for the date, English for numbers
Another option would be to load the text, parse the fields using the proper locale then export them in the format required by the next program.
Finally, a regular expression could be used to match only the numeric fields and remove the dot. This can be a bit tricky and depends on the actual contents.
For example (\d+)\.(\d{3}) can be used to match numbers if there is only one thousand separator. This can fail if some text field contains similar values. Or ;(\d+)\.(\d{3}); could match only a full field, except the first and last fields, eg:
Regex.Replace("1.457;2016.12.30;13.000;1,50;2015.12.04;13.456",#";(\d+)\.(\d{3});",#"$1$2;")
produces :
1.457;2016.12.3013000;1,50;2015.12.04;13.456
A regular expression that would match either numbers between ; or the first/last field could be
(^|;)(\d+)\.(\d{3})(;|$)
This would produce 1457;2016.12.30;13000;1,50;2015.12.04;13456, eg:
var data="1.457;2016.12.30;13.000;1,50;2015.12.04;13.456";
var pattern=#"(^|;)(\d+)\.(\d{3})(;|$)";
var replacement=#"$1$2$3$4";
var result= Regex.Replace(data,pattern,replacement);
The advantage of a regex over splitting and replacing strings is that it's a lot faster and more memory efficient. Instead of generating temporary strings for each split, manipulation, a Regex only calculates indexes in the source. A string object is generated only when you request the final text result. This results in far fewer allocations and garbage collections.
Even in medium-sized files this can result in 10x better performance

I wouldn't rely on the number of dots as mistakes can be made.
You can use the double.TryParse to safely test if the string is a number
var data = "2015.12.01;13.100;500;1.200;100;";
var dataArray = data.Split(';');
foreach (var s in dataArray)
{
double result;
if(double.TryParse(s,out result))
// implement your logic here
Console.WriteLine(s.Replace(".",string.Empty));
}

C# - Set excel cell with a formula containing double quotes

I'm trying to set via c# code the formula of an excel cell.
I use Microsoft.Office.Interop.Excel, version 14.
I always get an excel error 0x800A03EC, which is a kind of generic error.
String formula = "=IF(A2=\"BLANCO\";\"\";C1+1)"
Range cell = (Microsoft.Office.Interop.Excel.Range)ws.Cells[2, 3];
cell.Formula = formula;
I also tried to escape the double quotes with an #
String formula = #"=IF(A2=""BLANCO"";"""";C1+1)"
Same error, same problem.
When I try to set a simple formula, where no quotes are involved it is working fine.
Anybody has a solution?

Don't have much context for your code, but slashes should work when used appropriately. I am not sure about the use of semicolons here.
This code is an example pulled straight from one of my Interop programs and works fine:
thisExcel.xlWorksheet.Range["AD44", Type.Missing].Value = "=IF(BULK!L7=\"#N/A Field Not Applicable\",\"( \"&'Title Look Up'!C3&\" )\",\"( \"&'Title Look Up'!C3&\" )\")";
If all you want is: 'if a2 reads blanco then nothing else increment value of c1 by 1', then you just need:
=IF(A2=\"BLANCO\",\"\",C1+1)
I would also try using .Value rather than .Formula.
Hope that help

Building upon #getglad's answer - Using a slash does work for double quotes.
My recent solution (as of 2020):
worksheet.Cells[row,col].Value = "=IFERROR(VLOOKUP(etc),\"\")";

Copy numeric codes to clipboard and paste to Excel without having them formatted as numbers

I have a .NET Windows Forms applications and I need to copy a list of 8-digit numeric codes into the clipboard to be pasted to Excel sheet.
string tabbedText = string.Join("\n", codesArray);
Clipboard.SetText(tabbedText);
The problem is that when a code begins with one or more zeros (ex. "00001234") it's pasted as number with the zeros trimmed.
Is there a way how to set clipboard text so that Excel accepts it as text?

I would treat this problem inside of Excel (and not in your application programaticaly). Format your cells to be treated as text, and then paste from clipboard. This way leading zeros are always pasted.

EDIT: This doesn't work in Excel, in that the apostrophe gets pasted in and shows up too. I'm leaving the answer here as an explicit statement that this approach won't help for Excel.
It does work for OpenOffice Calc though.
The standard way to 'tell' Excel to treat a string as a string is to prefix it with an apostrophe. Have you tried something like:
string tabbedText = "'" + string.Join("\n'", codesArray);
(note the extra apostrophe in there... it's a bit hard to see).
Of course, this may cause you issues if you're planning to use this value thereafter in Excel calculations but there are ways to handle that too.

Query excel spreadsheet for cell format.... (percentage)

I am using the .Net 4.0 and excel 2003
How can i use an oledb connection to retrieve the cell format of an excel spreadsheet... I specifically want to find out if a cell column (or cell itself) is in a numeric percentage format.
I cannot seem to find this information in the GetOleDbSchemaTable method.
EX: My web app reads numbers from an excel spreadsheet. This works fine; However, if the numbers are in a percentage format, excel displays it as (fraction*100) but the actual value is a fractional decimal (1/3 = .3333..) - Excel displays as 33.33% - (Notice the decimal point).
Therefore, i need a way of distinguishing between what is a percentage & what is not to allow my webapp to work properly...
Any ideas?
Thanks in advance.....

You might be able to get out this information with OleDbConnection.GetSchema, but I'm not sure what information you'll get for an Excel sheet with that. Documentation here.

Search the NumberFormat property of the Cell (Range) in question for a % sign.
Also, if you can get the format type, then you're looking for a format that starts with 'P', like 'P1'.
EDIT: The only way I can see is either using XML or Automation. For automation you need to use the Interop Assembly. Namespace: Microsoft.Office.Interop.Excel, Interface: DisplayFormat, Property: NumberFormat.

Can you just read the first row of data as a string and parse it looking for '%' in the string.

How to show long numbers in Excel?

I have to build a C# program that makes CSV files and puts long numbers (as string in my program). The problem is, when I open this CSV file in Excel the numbers appear like this:
1234E+ or 1234560000000 (the end of the number is 0)
How I retain the formatting of the numbers? If I open the file as a text file, the numbers are formatted correctly.
Thanks in advance.

As others have mentioned, you can force the data to be a string. The best way for that was ="1234567890123". The = makes the cell a formula, and the quotation marks make the enclosed value an Excel string literal. This will display all the digits, even beyond Excel's numeric precision limit, but the cell (generally) won't be able to be used directly in numeric calculations.
If you need the data to remain numeric, the best way is probably to create a native Excel file (.xls or .xlsx). Various approaches for that can be found in the solutions to this related Stack Overflow question.
If you don't mind having thousands separators, there is one other trick you can use, which is to make your C# program insert the thousands separators and surround the value in quotes: "1,234,567,890,123". Do not include a leading = (as that will force it to be a string). Note that in this case, the quotation marks are for protecting the commas in the CSV, not for specifying an Excel string literal.

Format those long numbers as strings by putting a ' (apostrophe) in front or making a formula out of it: ="1234567890123"

You can't. Excel stores numbers with fifteen digits of precision. If you don't mind not having the ability to perform calculations on the numbers from within Excel, you can store them as Text, and all of the digits will display.

When I generate data to imported into Excel, I do not generate a CSV file if I want control over how the data are displayed. Instead, I write out an Excel file where the properties of the cells are set appropriately. I do not know if there is a library out there that would do that for you in C# without requiring Excel to be installed on the machine generating the files, but it is something to look into.

My two cents:
I think it's important to realize there is a difference between "Data" and "Formatting". In this example you are kind of trying to store both in a data-only file. This will, as you can tell from other answers, change the nature of the data. (In other words cause it to be converted to a string. A CSV file is a data only file. You can do some tricks here and there to merge formatting in with data, but to my way of thinking this essentially corrupts the data by merging it with non-data values: ie: "Formatting".
If you really need to be able to store formatting information I suggest that, if you have time to develop it out, you switch to a file type capable of storing formatting info separately from the data. It sounds like this problem would be a good candidate for a XML Spreadsheet solution. In this way you can not only specify your data, but also it's type and any formatting you choose to use.