How to find string of 4 or more character in other string

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if textbox1 contains string if any 4 or more continuous character from textbox1 are matches with string in textbox2 then wont allow it.
e.g
textbox1.text = copythiscode
textbox2.text = thisistext
wont allow. Because textbox2 contains "this"
i.e textbox2 Does not contains any combination of 4 or more characters from textbox1.

Posted 18-May-11 1:05am

bipin9

Updated 18-May-11 20:13pm

v6

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Olivier Levrey 18-May-11 7:26am

I don't understand why you split your string if you don't want to separate the words...
Can you give an example of what you want to do?

bipin9 18-May-11 8:40am

thank you

Kim Togo 18-May-11 9:00am

Hi bipin9
If the solution has help you and you do not have any other questions. Then please press "Accept Answer"

Olivier Levrey 18-May-11 9:38am

OP updated his question. Please see.

bipin9 18-May-11 9:29am

private void button2_Click(object sender, EventArgs e)
{
if (textBox2.Text.Length < 4)
{
textBox3.Text = "Password should be atleatst 4 character long";
}
else
{
findoccurance(textBox1.Text, textBox2.Text);
}

}
private void findoccurance(string source, string target)
{
if (source.Contains(target))
{
Console.Write("string contains {0}", target);
}
}

Kim Togo 18-May-11 9:50am

See my updated answer. Remember to use "Add Comment" under the solution or else I do not get any email on your question.

Kim Togo 19-May-11 5:34am

See my updated answer.

2 solutions

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Kim Togo · Accepted Answer · 2011-05-18T01:35:00

Based on updates from OP.

Try this regex string: (\w{3,})(?=.+\1)
This will find repeating words that is at least 3 char long or more disregards spacing.

C#

private bool CheckForRepeating(string text)
{
  return System.Text.RegularExpressions.Regex.IsMatch(text, @"(\w{3,})(?=.+\1)", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
}

// Test of method
bool test1 = CheckForRepeating("copythiscode");
// test1 is false

bool test2 = CheckForRepeating("copythiscodethisistext");
// test2 is true

You can do something like

C#

// any combination of 4 or more characters
bool test3 = CheckForRepeating(textbox1.Text + textbox2.Text);

If there is any repeating words from textbox1 in textbox2, this should make test3 = true.

----

You what to play with this regex string: (\w)\1{3}
It finds any alphanumeric with exact 4 repeating char.

Check out this great tool Expresso[^].

You can make a method that do a check like this.

C#

private bool CheckForRepeating(string text)
{
  return System.Text.RegularExpressions.Regex.IsMatch(text, @"(\w)\1{3}");
}

// Test of method
bool test1 = CheckForRepeating("password");
// test1 is false

bool test2 = CheckForRepeating("paaaassword");
// test2 is true

lukeer · Accepted Answer · 2011-05-18T04:13:00

Am I right with this
1. Textbox1 is for user name.
2. Textbox2 is for password.
3. Password must be at least 4 characters long.
4. Password must not contain user name.

You did the length constrain (3.) yourself.
For (4.) this would do:

System.Text.RegularExpressions.MatchCollection matchCollection = System.Text.RegularExpressions.Regex.Matches(textbox2.Text, textbox1.Text);
if(matchCollection.Count > 0)
  Console.WriteLine("Password contains user name.");

How to find string of 4 or more character in other string

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