i want to use Regex.IsMatch to find TB, GB, MB in VB.net Visual Basic - vb.net

Question

I have a textbox which i need to validate for the below entries and also need to replace
"3 GB" valid input
"3.2 GB" valid input
"3.2GB" valid input >> then replace as "3.2 GB"
"3.2" invalid input, ask for follow correct format MsgBox("follow the format like: 1 TB or 1.1 TB, 1 GB, 10 MB")
"VGGGB" invalid input, ask for follow correct format MsgBox("follow the format like: 1 TB or 1.1 TB, 1 GB, 10 MB")
Sub Main()
Dim input = Console.ReadLine().ToUpper()
Dim nInput, value
Dim ChkDecimal As Double
If input IsNot "" Then
If input.EndsWith("TB") Then
nInput = input.Replace("TB", "")
If nInput IsNot vbNullString And IsNumeric(nInput) Then
value = Convert.ToDouble(nInput)
value = CDbl(value * 1048576 + 1)
ChkDecimal = FormatNumber(CDbl(value / 1048576), 2) Mod 1 ' check the number has a valid Decimal value
If ChkDecimal = 0 Then
Console.WriteLine(FormatNumber(CDbl(value / 1048576), 0) & " TB")
Else
Console.WriteLine(FormatNumber(CDbl(value / 1048576), 2) & " TB")
End If
Else
Console.WriteLine("Invalid format!! should like: 99.99 MB/GB/TB")
End If
ElseIf (input.EndsWith("GB")) Then
nInput = input.Replace("GB", "")
If nInput IsNot vbNullString And IsNumeric(nInput) Then
value = Convert.ToDouble(nInput)
value = CDbl(value * 1024)
ChkDecimal = FormatNumber(CDbl(value / 1024), 2) Mod 1 ' check the number has a valid Decimal value
If ChkDecimal = 0 Then
Console.WriteLine(FormatNumber(CDbl(value / 1024), 0) & " GB")
Else
Console.WriteLine(FormatNumber(CDbl(value / 1024), 2) & " GB")
End If
Else
Console.WriteLine("Invalid format!! should like: 99.99 MB/GB/TB")
End If
ElseIf input.EndsWith("MB") = True Then
nInput = input.Replace("MB", "")
If nInput IsNot vbNullString And IsNumeric(nInput) Then
value = Convert.ToDouble(nInput)
value = CDbl(value * 1)
Console.WriteLine(FormatNumber(CDbl(value * 1), 0) & " MB")
Else
Console.WriteLine("Invalid format!! should like: 99.99 MB/GB/TB")
End If
Else
Console.WriteLine("Invalid format!! should like: 99.99 MB/GB/TB")
End If
Else
Console.WriteLine("Capacity input Format: 99.99 MB/GB/TB")
End If
End Sub

Answer 1

I wouldn't use a regular-expression for this, because there's a much simpler (and more robust!) approach described below.
If you do use a regular-expression, you'll need to add all of the unit names to the expression, which is painful. Regular-expressions are not well-suited to accepting a large list of possible literal inputs.
Using a regular-expression would also mean the input would not be culture-aware, which is bad for usability (as many places around the world swap the , and . glyphs in numbers) - and you really don't want to handle things like digit-grouping, etc.
Instead, first extract and validate the unit name, then parse the numeric value using Decimal.TryParse
Like so (using C# because it's 2am here and I'm not getting paid to write this answer):
void Example()
{
String textBoxValue = "3 GB";
if( TryParseBinaryDataQuantity( textBoxValue, out Int64 valueBytes ) )
{
MessageBox.Show( "Visual Basic is dead." );
}
else
{
MessageBox.Show( "Input is not a valid binary data quantity." );
}
}
public static Boolean TryParseBinaryDataQuantity( String input, out Int64 valueBytes )
{
input = ( input ?? "" ).Trim();
if( input.Length < 3 ) // input is too short to be meaningful.
{
valueBytes = default;
return false;
}
// Extract the unit-name by taking the last 3 characters of the input string and trimming any whitespace (this isn't the most robust or correct approach, but I'm feeling lazy):
String unitName = input.Substring( startIndex: input.Length - 3 );
// Validate the unit-name and get the bytes multiplier:
if( !TryParseBinaryDataUnit( unitName, out Int64 multiplier ) )
{
valueBytes = default;
return false;
}
// Consider repeating the above but for the last 2 characters of the string in order to match input like "3GB" instead of "3GiB" and "3 GB" and "3 GiB".
// Parse and multiply:
String numberPart = input.Substring( startIndex: 0, length: input.Length - 3 );
if( Decimal.TryParse( numberPart, NumberStyles.Any, CultureInfo.CurrentCulture, out Decimal quantity )
{
Decimal bytesValue = quantity * multiplier;
// Fail if the bytesValue is non-integral or negative:
if( bytesValue != Math.Floor( bytesValue ) || bytesValue < 0 )
{
valueBytes = default;
return false;
}
return (Int64)bytesValue;
}
}
private static Boolean TryParseBinaryDataUnit( String unitName, out Int64 equivalentBytes )
{
if( "GB".Equals( unitName, StringComparison.CurrentCultureCaseInsensitive ) )
{
equivalentBytes = 1024 * 1024 * 1024; // or 1000 * 1000 * 1000 depending on if you're differentiating between GiB and GB.
return true;
}
else if( "GiB".Equals( unitName, StringComparison.CurrentCultureCaseInsensitive ) )
{
equivalentBytes = 1024 * 1024 * 1024;
return true;
}
else if( "MiB".Equals( unitName, StringComparison.CurrentCultureCaseInsensitive ) )
{
equivalentBytes = 1024 * 1024;
return true;
}
else if( "MB".Equals( unitName, StringComparison.CurrentCultureCaseInsensitive ) )
{
equivalentBytes = 1024 * 1024;
return true;
}
else if( "KB".Equals( unitName, StringComparison.CurrentCultureCaseInsensitive ) )
{
equivalentBytes = 1024;
return true;
}
else if( "KB".Equals( unitName, StringComparison.CurrentCultureCaseInsensitive ) )
{
equivalentBytes = 1024;
return true;
}
else
{
equivalentBytes = default;
return false;
}
}

Answer 2

I will recommend you to use proper library to parse the given input. I have used one in past for doing this (https://github.com/omar/ByteSize)
Here is quick example of how you can do this. I know there must be better way to do this but this would do the job =)
var input = Console.ReadLine();
input = input.ToLower();
var reg = Regex.Match(input, "([\\d\\.]+)");
if (reg.Success && double.TryParse(reg.Groups[1].Value, out double rawSize))
{
if (input.EndsWith("tb"))
Console.WriteLine(ByteSize.FromTeraBytes(rawSize));
else if (input.EndsWith("gb"))
Console.WriteLine(ByteSize.FromGigaBytes(rawSize));
else if (input.EndsWith("mb"))
Console.WriteLine(ByteSize.FromMegaBytes(rawSize));
else if (input.EndsWith("kb"))
Console.WriteLine(ByteSize.FromKiloBytes(rawSize));
}
Input> 1234.56mb
Output> 1.23 GB

Answer 3

You can try my method as following:
Imports System.Text.RegularExpressions
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'1.3 GB
'1.3gb
'1gb
Console.WriteLine("Pleasen input your entry:")
Dim str As String = TextBox1.Text
Dim str1 As String = str.Substring(str.Length - 2, 2)
If str1.ToUpper = "TB" Or str1.ToUpper = "GB" Or str1.ToUpper = "MB" Then
Dim str2 As String = str.Remove(str.Length - 2)
Dim str3 As String = str.Substring(str2.Length - 1, 1)
If str3 = " " Then
Dim str4 As String = str.Remove(str.Length - 3)
If Regex.IsMatch(str4, "^\d*[.]?\d*$") Then
MsgBox("valid input")
Else
MsgBox("follow the format like: 1 TB or 1.1 TB, 1 GB, 10 MB")
Return
End If
Else
If Regex.IsMatch(str2, "^\d*[.]?\d*$") Then
TextBox1.Text = str.Insert(str.Length - 2, " ")
MsgBox("valid input")
Else
MsgBox("follow the format like: 1 TB or 1.1 TB, 1 GB, 10 MB")
Return
End If
End If
Else
MsgBox("follow the format like: 1 TB or 1.1 TB, 1 GB, 10 MB")
Return
End If
End Sub
End Class