Get boolean value from database for ASP.NET C#

public bool getActiveUser(string UserName,string Password) {
DBAccess cmd = new DBAccess();
string sql = "select isactivate from tblusers where username='" + clsUtilities.sqlStr(this.UserName.Text) + "' and [password]='" + clsUtilities.sqlStr(this.Password.Text) + "'";
bool i = (bool) cmd.ExecuteScalar(sql);
if (i==true)
{
return true;
}
else
{
return false;
}
}