How to make a specific regex for C#?

[AsleeKaizoku]

Im trying to make a regular expresion which...

1) Consist of at least one non alphanumeric character (not including white spaces)
2) At least 7 characters long


So it would match something like...

Hello!1
P@ssword

but not:

Hello1 1
Password111

[Magos]

Alphanumeric characters are "[a-zA-Z0-9]", so non-alphanumeric would be "[^a-zA-Z0-9]".
You don't mention any rules of the oterh characters, so I'll assume almost any can do. This is the pattern ".".
The final expression could then be ".*[^a-zA-Z0-9].*".
Note that * is greedy (look this up!) so you may need to use ".*?" instead of ".*", but I don't think it matters in this case.
As for the length of at least 7 it gets a little trickier. Can't you just check the length in code?

[AsleeKaizoku]

Can't you just check the length in code?

Ahhh! Bloddy hell, why didn't I think of that? That makes it so much easier

Regex regexPassword = new Regex(@".*[^a-zA-Z0-9].*");
if (!regexPassword.IsMatch(txtPass.Text.ToString().Trim()))
{
  lblError.Text = "  * Must have at least 1 non-alphanumeric character";
  lblError.Visible = true;
}
else if (regexPassword.IsMatch(txtPass.Text.ToString().Trim()))
{
  string temp = txtPass.Text.ToString().Trim();
  if (temp.Length < 7)
  {
    lblError.Text = "&nbsp;&nbsp;* Password length minimum: 7.";
    lblError.Visible = true;
  }
}

Thanks a bunch

[Magos]

A few notes:

1) your "else if" is unneccessary, just an "else" will do (you perform that check already in the "if")
2) No need to call ToString() on TxtPass.Text, it is already a string

[AsleeKaizoku]

A few notes:

1) your "else if" is unneccessary, just an "else" will do (you perform that check already in the "if")
2) No need to call ToString() on TxtPass.Text, it is already a string

Oh yeah, (1) its a direct snippet from my code so, there are actually a bunch of other else ifs later on.

(2) I keep forgetting that :P

[Cat]

You also said you wanted whitespace characters to not count.

I'd do @".*[^a-zA-Z\s\d].*" for your regex. Anything that's not a letter, whitespace, or number.