In this article I will explain with an example, how to generate unique Random Strings containing Letters and Numbers (AlphaNumeric) and Numbers (Numeric) in ASP.Net using C# and VB.Net.
The unique Random Strings containing Letters and Numbers (AlphaNumeric) and Numbers (Numeric) will be generated in variable lengths such as 5, 8 and 10 characters in ASP.Net using C# and VB.Net.
HTML Markup
The following HTML Markup consists of an ASP. Net DropDownList, a RadioButtonList, a Button and a Label.
The DropDownList contains the Length options and the RadioButtonList contains the Alphanumeric and Numeric options.
<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td>
<asp:DropDownList ID="ddlLength" runat="server">
<asp:ListItem Text="5" Value="5" />
<asp:ListItem Text="8" Value="8" />
<asp:ListItem Text="10" Value="10" />
</asp:DropDownList>
</td>
<td>
<asp:RadioButtonList ID="rbType" runat="server" RepeatDirection="Horizontal">
<asp:ListItem Text="Alphanumeric" Value="1" Selected="True" />
<asp:ListItem Text="Numeric" Value="2" />
</asp:RadioButtonList>
</td>
<td>
<asp:Button ID="btnGenerate" Text="Generate OTP" runat="server" OnClick="GenerateOTP" />
</td>
</tr>
<tr>
<td>
</td>
</tr>
<tr>
<td colspan="3">
OTP:
<asp:Label ID="lblOTP" runat="server" />
</td>
</tr>
</table>
Generate Unique Random Strings containing Letters and Numbers (AlphaNumeric) and Numbers (Numeric) in ASP.Net
When the Button is clicked, the length and the type values of the Password are fetched from the DropDownList and RadioButtonList.
There are three strings, first containing Upper Case Alphabets, second containing Lower Case Alphabets and the third one containing the 10 digits.
Then a loop is executed and inside the loop a
random number is used to fetch the character from the combination of Alphabets
and Numeric strings or only the Numeric string based on the type selected in the RadioButtonList.
Inside the For Loop, a While loop is used to avoid repetition of the characters.
The generated unique random string is displayed in the Label control.
C#
protected void GenerateOTP(object sender, EventArgs e)
{
string alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
string small_alphabets = "abcdefghijklmnopqrstuvwxyz";
string numbers = "1234567890";
string characters = numbers;
if (rbType.SelectedItem.Value == "1")
{
characters += alphabets + small_alphabets + numbers;
}
int length = int.Parse(ddlLength.SelectedItem.Value);
string otp = string.Empty;
for (int i = 0; i < length; i++)
{
string character = string.Empty;
do
{
int index = new Random().Next(0, characters.Length);
character = characters.ToCharArray()[index].ToString();
} while (otp.IndexOf(character) != -1);
otp += character;
}
lblOTP.Text = otp;
}
VB.Net
Protected Sub GenerateOTP(sender As Object, e As EventArgs)
Dim alphabets As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
Dim small_alphabets As String = "abcdefghijklmnopqrstuvwxyz"
Dim numbers As String = "1234567890"
Dim characters As String = numbers
If rbType.SelectedItem.Value = "1" Then
characters += Convert.ToString(alphabets & small_alphabets) & numbers
End If
Dim length As Integer = Integer.Parse(ddlLength.SelectedItem.Value)
Dim otp As String = String.Empty
For i As Integer = 0 To length - 1
Dim character As String = String.Empty
Do
Dim index As Integer = New Random().Next(0, characters.Length)
character = characters.ToCharArray()(index).ToString()
Loop While otp.IndexOf(character) <> -1
otp += character
Next
lblOTP.Text = otp
End Sub
Screenshot
![Generate Unique Random Strings containing Letters and Numbers (AlphaNumeric) and Numbers (Numeric) in ASP.Net using C# and VB.Net]()
Demo
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