Question

How to add decimal point (with two decimal places) to string, without converting string to decimal?

For example (Dim str1 as String), regardless str1 has value: 100 , 100.0 , 100.00, or 100.5 , 100.50…
I’d like to get the output: 100.00 or 100.50, with two decimal places.

Answer 1

Public Function FormatNumber(ByVal s As String) As String
    Dim pos As Integer = s.IndexOf("."c)
    If pos = -1 Then ' No decimal point
        Return s & ".00"
    Else
        Return (s & "00").Substring(0, pos + 3)
    End If
End Function

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And since you inserted a C# tag:

public string FormatNumber(string s)
{
    int pos = s.IndexOf('.');
    if (pos == -1) { // No decimal point 
        return s + ".00";
    } else {
        return (s + "00").Substring(0, pos + 3);
    }
}

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However, note that superfluous decimals will be truncated – no rounding occurs!