c# - How to check whether a string contains any special character

Check whether a String contains any special character
The String represents text as a sequence of UTF-16 code units. The String is a sequential collection of characters that is used to represent text. The String is a sequential collection of System.Char objects.

The following .net c# tutorial code demonstrates how we can check whether a String object contains any special character. In this .net c# tutorial code we will determine whether a String instance contains any special character. Here we do this using regular expressions.

The Regex represents an immutable regular expression. The Regex() initializes a new instance of the Regex class. The Regex(String, RegexOptions) constructor initializes a new instance of the Regex class for the specified regular expression with options that modify the pattern.

So, using the Regex(String pattern, RegexOptions options) method we can check whether a String object contains any special character or not. We have to pass the specified regular expression to the method as the pattern. We also pass the RegexOptions.IgnoreCase for the options parameter.

The Regex IsMatch() method indicates whether the regular expression finds a match in the input String. This method returns a Boolean value. It returns true if the regular expression finds a match otherwise it returns false.
string-contains-special-characters.aspx

<%@ Page Language="C#" AutoEventWireup="true"%>

<!DOCTYPE html>  
<script runat="server"> 
    protected void Button1_Click(object sender, System.EventArgs e)  
    {
        //this section create string variables.
        string colors = "1 Red 2 green 3 blue";
        string colors2 = "#red #green #blue";
        string colors3 = "red* green* blue*";

        Label1.Text = "string..................<br />";
        Label1.Text += "colors: " + colors;
        Label1.Text += "<br />colors2: " + colors2;
        Label1.Text += "<br />colors3: " + colors3;

        //check string contains any special characters without space
        Regex rex = new Regex("^[a-z0-9 ]+$",RegexOptions.IgnoreCase);

        Boolean result = rex.IsMatch(colors);
        Boolean result2 = rex.IsMatch(colors2);
        Boolean result3 = rex.IsMatch(colors3);

        Label1.Text += "<br /><br />colors contains no special characters without space? " + result.ToString();
        Label1.Text += "<br /><br />colors2 contains no special characters without space? " + result2.ToString();
        Label1.Text += "<br /><br />colors3 contains no special characters without space? " + result3.ToString();
    }  
</script>  
  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head id="Head1" runat="server">  
    <title>c# example - string contains special characters</title>  
</head>  
<body>  
    <form id="form1" runat="server">  
    <div>  
        <h2 style="color:MidnightBlue; font-style:italic;">  
            c# example - string contains special characters
        </h2>  
        <hr width="550" align="left" color="Gainsboro" />  
        <asp:Label   
            ID="Label1"   
            runat="server"  
            Font-Size="Large"
            >  
        </asp:Label>  
        <br /><br />
        <asp:Button   
            ID="Button1"   
            runat="server"   
            Text="string contains special characters"  
            OnClick="Button1_Click"
            Height="40"  
            Font-Bold="true"  
            />  
    </div>  
    </form>  
</body>  
</html>
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