asp.net C#如何实现验证码不区分大小写

string a="验证码字符串"
string b="要输入的字符串";
if (a.Equals(b, StringComparison.OrdinalIgnoreCase))
{
Response.Write("<script>alert('验证码输入成功')</script>");
}
else
{
Response.Write("<script>alert('验证码输入失败')</script>");
}

转换成大写或小写比较，如转换成小写:

string a = "用户输的";
string b = "验证码";

if(a.ToLower () == b.ToLower () )
{
//OK
}

string a = "用户输的";
string b = "验证码";

if(a.Equals(b, StringComparison.OrdinalIgnoreCase)
// 正确
statement..
else
// 错