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C# String format: escape a dot

I have a line of code, something like:
mbar.HealthLabel.text = String.Format("{0:0.0}", _hp);
Output is: 2.25 for example. Is it possible to escape a dot from the output string view with String.Format function ?
For. ex. 225,
To make my question more clear, I need the same effect like:
Math.Floor(_hp * 100).ToString();
But need to do it by String.Format template.. Thanks.

Simply you can do it this way
double value = 1.25;
var stringValue = string.Format("{0:0}", value * 100, CultureInfo.InvariantCulture); //125
EDIT:
More general solution would be to Replace the dot with empty string as stated in the comments.
double value = 1.25;
var stringValue = value.ToString(CultureInfo.InvariantCulture).Replace(".",string.Empty);
EDIT2: Also there is another general idea that do not use Replace function (but also it does not use the String.Format)
var stringValue = string.Join("", value.ToString().Where(char.IsDigit));
Also another similar idea:
var stringValue = new string(value.ToString().Where(char.IsDigit).ToArray());

First of all, please read my comment to the question. As i mentioned there, string format for numeric values depends on regional settings. So, below line
mbar.HealthLabel.text = String.Format("{0:0.0}", _hp);
will return: 2,25 (as to the polish numeric standard)
In my opinion you need something like this:
mbar.HealthLabel.text = String.Format("{0:D}", Math.Floor(_hp*100));
For furhter details, please see:
Standard Numeric Format Strings
Custom Numeric Format Strings

Up to Microsoft.NET Framework 4.7 there is no way to solve this when we are only allowed to modify the format string ("template"). All solutions require to either:
Post-process the resulting string. Here, the closest for the special case with two decimals may be the % format
Compute the numeric argument first to make it integer
Write and apply a custom IFormatProvider implementation

If you want to eliminate the decimal separtor ("escape the dot", as you've put it), try replacing the decimal separator with empty string:
string result = String
.Format("{0:0.0}", _hp)
.Replace(CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator, "");

C# - Format float WITHOUT tail zeros

Is that possible in C# to format
4.52 float number to 4.52 string
and
4.520 float number to 4.52 string, i.e. omitting tail zeros?
EDIT: I think I've not accented the real problem.
I need ONE pattern that conforms BOTH of the above examples!

Assuming you want to omit any trailing 0's from your value, this should give you what you want:
ToString("0.####")
Otherwise you could do:
ToString("0.00##")

See this website for examples.
i.e
String.Format("{0:0.00}", 4.520); // "4.52"

Actually, you don't need a pattern. .NET always omits the tail zeros of float numbers, unless specified to do not.
So Console.WriteLine(4.520) would output 4.52, as would Console.WriteLine(4.52) or Console.WriteLine(4.520000000000), as Console.WriteLine(4.5) would output 4.5.
In the example above, the System.Console.WriteLine method will internally call ToString() (with no patterns) on your float number.
Also, if you're looking for something more specific, you can take a look at
http://msdn.microsoft.com/en-us/library/dwhawy9k(v=vs.71).aspx
for some more number format strings.

All of these result in "4.52":
string formatted = 4.52.ToString();
string formatted = 4.520.ToString();
Because that was too easy I wonder if maybe your float is really a string:
string formatted = "4.52".Trim('0');
string formatted = "4.520".Trim('0');

Formatting currency in .NET

I am formatting the currency using Tostring() method i m using following syntax
ToString('##.##') it is working perfectly but in case of round number it remove last 2 zero
like for 100 it does not show 100.00 is shows 100.
how can i format in that way means
input desired output
100 100.00
100.10 100.10

Try "##.00" instead.
That will force two digits after the decimal separator.
You can also use ToString("C") to use the culture specific format in Windows directly.

First google result.
String.Format("{0:C}", x.ToString());
http://www.howtogeek.com/howto/programming/format-a-string-as-currency-in-c/

You can use :
.ToString("C")
Hope it helps.

Also, if you don't want the currency sign ($ in the US) added that "C" gives, you can also use "F2", which is "fixed number with 2 decimal places". It also has the advantage of giving you a thousands separator when you results go over 1,000.00.

This might help. Might be more than you need, but it takes globalization into account which might be necessary. "C" is also a short-cut currency format string that might get you further along.

Number Formatting in Thousands

How, for example, do I turn the number 10562.3093 into 10,562 in C#?
Also, how do I ensure that same formatter will apply correctly to all other numbers?....
...For example 2500.32 into 2,500
Help greatly appreciated.

string formatted = value.ToString("N0");
This divides your number in the manner specified by the current culture (in the case of "en-US," it's a comma per multiple of 1000) and includes no decimal places.
The best place to look for any question regarding formatting numbers in .NET would have to be here:
Standard Numeric Format Strings (MSDN)
And here:
Custom Numeric Format Strings (MSDN)

string.Format("{0:n0}", 10562.3093);

String.Format("{0:0,0}", 10562.3093);
I keep this website bookmarked for these purposes: String Formatting in C#

double x = 10562.3093;
x.ToString("#,0");
or
String.Format("{0:#,0}", 10562.3093);

VB.NET FormatNumber equivalent in C#?

Is there a C# equivalent for the VB.NET FormatNumber function?
I.e.:
JSArrayString += "^" + (String)FormatNumber(inv.RRP * oCountry.ExchangeRate, 2);

In both C# and VB.NET you can use either the .ToString() function or the String.Format() method to format the text.
Using the .ToString() method your example could be written as:
JSArrayString += "^" + (inv.RRP * oCountry.ExchangeRate).ToString("#0.00")
Alternatively using the String.Format() it could written as:
JSArrayString = String.Format("{0}^{1:#0.00}",JSArrayString,(inv.RRP * oCountry.ExchangeRate))
In both of the above cases I have used custom formatting for the currency with # representing an optional place holder and 0 representing a 0 or value if one exists.
Other formatting characters can be used to help with formatting such as D2 for 2 decimal places or C to display as currency. In this case you would not want to use the C formatter as this would have inserted the currency symbol and further separators which were not required.
See "String.Format("{0}", "formatting string"};" or "String Format for Int" for more information and examples on how to use String.Format and the different formatting options.

Yes, the .ToString(string) methods.
For instance,
int number = 32;
string formatted = number.ToString("D4");
Console.WriteLine(formatted);
// Shows 0032
Note that in C# you don't use a number to specify a format, but you use a character or a sequence of characters.
Formatting numbers and dates in C# takes some minutes to learn, but once you understand the principle, you can quickly get anything you want from looking at the reference.
Here's a couple MSDN articles to get you started :
Standard Numeric Format Strings
Formatting Types

You can use string formatters to accomplish the same thing.
double MyNumber = inv.RRP * oCountry.ExchangeRate;
JSArrayString += "^" + MyNumber.ToString("#0.00");

While I would recommend using ToString in this case, always keep in mind you can use ANY VB.Net function or class from C# just by referencing Microsoft.VisalBasic.dll.