Hi
I completed my project work . , but only one problem is Sql injection. For this project I used asp.net platform with c#.

I need to compare each letters in the textbox value., if thre has any letters like <,>,.,!,<!,create ,etc..then the the error message should display.
For that i wrote If(String.Compare(text_compname.text,"<"))
{
lablel1.visible=true; // lbale1=" Invalid Charrecter"
}
else
{
// regular statements
}
When Run the program with this code there is an error like "cannot implicitly convert type'int' to 'bool'

can u find any mistake in this code?????

weather there has any other coding for string comparison in asp.net with c#??

please help me............

if(text_compname.Text.Contains("<"))
// handle the invalid character

Each string is an instance of the String class which has MANY methods attached to it that you can use for all kinds of string search and manipulation. Familiarize yourself with them.

using System.Text.RegularExpressions; 

public class Test 
{ 
    MatchCollection matchtag; 
    MatchCollection wordsmatchcoll; 
 

private void method()
   { 
        wordsmatchcoll = Regex.Matches(RichTextBox1.Text, "<", RegexOptions.IgnoreCase); 
        if (wordsmatchcoll.Count > 0) 

        { 
            Interaction.MsgBox("Text is having some special characters"); 
        } 
    } 
} 

Here method is the event in which you are trying to compare the strings.

Mark the reply as answer if it helps you to solve your problem

Cheers:)

Based on the original post, I agree that Regex is a good approach. The original post said that there were multiple characters that should trigger failure. The Regex pattern is designed to do that...

if ( Regex.IsMatch(textbox1.Text, @"(\bcreate\b|\<\!|[<>.!])") ==true )
{
// fail gracefully
MessageBox.Show("The text containsinvalid symbols or words");
}

Ignore my previous update.

To compare the string with special characters can be achived by using match collection function which will provide the count of the special characters present in the string.

matchcolletion wordsmatchcoll = default(matchcolletion); 
    
    wordsmatchcoll = Regex.Matches(TextBox1.Text, "(\\bcreate\\b|\\<\\!|[<>.!])", RegexOptions.IgnoreCase); 
    
    if (wordsmatchcoll.Count > 0) { 
        
            
        Interaction.MsgBox("Text is having " + wordsmatchcoll.Count + " special characters"); 
    } 
<br/><br/><br/>

Ignore my previous update.

To compare the string with special characters can be achived by using match collection function which will provide the count of the special characters present in the string.

matchcolletion wordsmatchcoll = default
(matchcolletion); 
    
    wordsmatchcoll = Regex.Matches(TextBox1.Text, "(\\bcreate\\b|\\<\\!|[<>.!])"
, RegexOptions.IgnoreCase); 
    
    if
 (wordsmatchcoll.Count > 0) { 
        
            
        Interaction.MsgBox("Text is having "
 + wordsmatchcoll.Count + " special characters"
); 
    } 
<br/><br/><br/>

Thanks Rohini,
But This Vs2003 software,there is some problems.. In My VS2003 software the validation controlls does not work..such as regular expression validator, required field validator etc....if the regular expression validator is required for this coding???
please reply meeee

Thanks in Advance

Regular expression is not a validator control.

To make use of those function, you have to import regular expression namespace.

using System.Text.RegularExpressions;

Try touse this namespace, which helps you to solve your problem.

cheers:)