登录时，验证码不区分大小写进行验证 || 字符串比较时不区分大小写

string showCode = "验证码字符串"
string writeCode = "要输入的字符串";
if (showCode.Equals(writeCode, StringComparison.OrdinalIgnoreCase))
{
    Response.Write("验证码输入成功！");
}
else
{
    Response.Write("验证码输入失败！");
}

 

2.去除字符串中的空格，回车，换行符，制表符

string strResult = str.Replace("\n", "").Replace(" ","").Replace("\t","").Replace("\r","");