string  SomeString =   hello // abc; 
正则表达式r = 新正则表达式（  ^ [A-ZA-Z0-9] * 

跨度>）;
if （r.IsMatch（SomeString））
{
lbl_valid.Text = 有效;
}
else
{
lbl_valid.Text = In-Valid;
}

尝试：

  private   bool  isvalidString（ string  str）
 {
 return ！str.Contains（ @  //）; 
} 

i have a problem which i have solved but i am searching for better solution.
my problem is i have a string say

string mystr = "hello//abc";

if string contain continuously two or more slash like above string it is invalid string

What I have tried:

private bool isvalidString(string str) 
        {
            int i = 0;
            int lastIndex = -2;
            bool retvalue = true;
            do
            {
                i = str.IndexOf("/", i + 1);
                if (lastIndex + 1 == i)
                {
                    retvalue = false;
                    break;
                }
                lastIndex = i;
                if (i==-1)
                {
                    break;
                }
   
            } while (true);


            return retvalue;
        }

string SomeString = "hello//abc";
           Regex r = new Regex("^[a-zA-Z0-9]*

"); if (r.IsMatch(SomeString)) { lbl_valid.Text = "Valid"; } else { lbl_valid.Text = "In-Valid"; }

Try:

private bool isvalidString(string str) 
    {
    return !str.Contains(@"//");
    }