Incorrect syntax near 's'. Unclosed quotation mark after the character string

Hi all,
Thanks to all for giving me suggestion in completion of my project. But i struck with one issue which was asked by friend in my project. I hope someone can help me out to solve the issue. below is my issue.
I am unable to login a username with name test's, getting below error. I am posting my code also. Please let me know how to solve the issue.
Error
Incorrect syntax near 's'. Unclosed quotation mark after the character string
Code:
SqlCommand cmmd = new SqlCommand("select count(*) from VirtualCRM where name='" + user_login_details.Username_value + "' and password='" + user_login_details.pass_value + "'", conn); string str = cmmd.ExecuteScalar().ToString(); string loginUserid = cmmd.ExecuteScalar().ToString(); return str;
Thanks,
Laxman