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Decimal point lost in conversion

I have a string that contains: 2.53 and I'm trying to convert this number into decimal type, so I did:
string value = "2.53";
decimal converted = Convert.ToDecimal(value);
but the final result is: 253

Decimal point is different in every culture. In your culture it might be a comma. You can use InvariantCulture which has dot as decimal separator:
decimal converted = Convert.ToDecimal(value, CultureInfo.InvariantCulture);

How to convert the double value to string without losing the data in c#

I have a double value as below
double propertyValue = 1994.7755474452554;
When i convert this double value to a string
string value = propertyValue.ToString();
it gives the value "1994.77554744526"
It has rounded off the last digits 2554 to 26.
But I do not want to round the value. Share your ideas.

By default the .ToString() method of Double returns 15 digits of precision. If you want the full 17 digits that the double value holds internally, you need to pass the "G17" format specifier to the method.
String s = value.ToString("G17");
This will prevent the rounding off of double value when converted to string.
value = propertyValue.ToString("G17");

You could use decimal type instead.
decimal propertyValue = 1994.7755474452554M;

I can't reproduce the misbehaviour; you've experienced a representation effect: it's ToString() puts double like that.
string source = "1994.7755474452554";
double d = double.Parse(source, CultureInfo.InvariantCulture);
string test = d.ToString("R", CultureInfo.InvariantCulture);
Console.Write(source.Equals(test) ? "OK" : "Rounded !!!");
Outcome is OK. Please, notice "R" format string:
The Round-trip ("R") Format Specifier
https://msdn.microsoft.com/en-us/library/dwhawy9k(v=vs.110).aspx#RFormatString

You can cast double to decimal and use the default ToString() like this:
Double propertyValue = 1994.77554744526;
var str = ((decimal)propertyValue).ToString();
//str will hold 1994.77554744526

Convert from exponential notation to non-exponential notation

I have tried:
MessageBox.Show(System.Numerics.BigInteger.Parse("7.56e+011",
NumberStyles.Float,
CultureInfo.InvariantCulture));
But it continues to show 7.56e+011

You are looking to format the number. You can use String.Format to do so
string.Format("{0:F}",System.Numerics.BigInteger.Parse("7.56e+011",
NumberStyles.Float,
CultureInfo.InvariantCulture))
Running the following code
Gives you the following MessageBox
you can specify no decimal points by changing it to {0:F0} for the format.

Try
BigInteger num = System.Numerics.BigInteger.Parse("7.56e+011",
NumberStyles.Float,
CultureInfo.InvariantCulture);
String text = num.ToString("F5"); // New format string, here with 5 digits.
Your solution does an implicit conversion from BigInteger back to string again, which uses the scientific notation if the exponent is large.

decimal dec = decimal.Parse("7.7583877127496407E-6",
System.Globalization.NumberStyles.Any);
Console.WriteLine(dec);

convert this string into decimal

Sounds easy but when I tried to achieve i'm stock about how is the formatter to make this conversion this are some examples of strings that i need to convert to decimal
00.24
48.34
01.24
Does anybody know how can i Accomplish this?? I tried like this
try
{
decimal x = Convert.ToDecimal("00.24", );
//Which formatter do I need to pass??
decimal x = Convert.ToDecimal("00.24", Formatter???);
}
Catch(Exception e)
{
throw new Exception()
}
But It doesn't work because the result it's 24D and i need 0.24D

I suspect your system culture is not English and has different number formatting rules. Try passing the invariant culture as the format provider:
decimal d = Convert.ToDecimal("00.24", CultureInfo.InvariantCulture);
You could also use Decimal.Parse:
decimal d = Decimal.Parse("00.24", CultureInfo.InvariantCulture);

Why not just use Decimal.Parse
decimal x = Decimal.Parse("00.24");
Console.WriteLine(x); // Prints: 00.24

I think Decimal.TryParse should work. More info here.

The result you're getting is because the dot . is tretaed as a group (thousand) separator. the parser simply discards it, and doesn't check if the group sizes are right. So '20.100.200' or '1.2.3.4' would also get parsed as 20100200 and 1234.
This happens on many european cultures, like 'es'
You have to use any culture that doesn't consider a . as a group separator, but as a decimal separator. CultureInfo.InvariantCulture is one of the possible cultures (it has basically the same configuration of en-US).

StringFormat Double without rounding

double d = toDateTime.SelectedDateTime.Subtract(
servicefromDateTime.SelectedDateTime).TotalHours;
string s = String.Format("{0:0}",d);
But the String.Format rounds up the value: if d is 22.91 the String.Format gives the rounding result of 23. I don't want to round up. For example, if d is 22.1222222, then I want 22. if d is 22.999999, then I want 22.
How can I achieve this?

You could use Math.Truncate
double d = toDateTime.SelectedDateTime.Subtract(servicefromDateTime.SelectedDateTime).TotalHours;
string s = String.Format("{0:0}", Math.Truncate(d));

If you cast the double to an int/long it will chop off any decimal component, effectively giving you a "floor" or round-down of the double.

Then you need to Math.Floor
double d = toDateTime.SelectedDateTime.Subtract(servicefromDateTime.SelectedDateTime).TotalHours;
string s = String.Format("{0:0}",Math.Floor(d));