HttpUtility.HtmlEncode doesn't encode everything

Question

I am interacting with a web server using a desktop client program in C# and .Net 3.5. I am using Fiddler to see what traffic the web browser sends, and emulate that. Sadly t

Answer 1

@bdukes response above will do the job, but we can make it much faster if we assume that most characters will not be in this range. Note the quoted 'Ā' (unicode 0x0100)

/// 
.Net 2.0's HttpUtility.HtmlEncode will not properly encode
/// Unicode characters above 0xFF.  This may be fixed in newer 
/// versions.
public static string HtmlEncode(string s)
{
    // Let .Net 2.0 get right what it gets right.
    s = HttpUtility.HtmlEncode(s);

    // Search for first non-ASCII.  Hopefully none and we can just 
    // return s.
    int num = IndexOfHighChar(s, 0);
    if (num == -1)
        return s;
    int old_num = 0;
    StringBuilder sb = new StringBuilder();
    do {
        sb.Append(s, old_num, num - old_num);
        sb.Append("&#");
        sb.Append(((int)s[num]).ToString(NumberFormatInfo.InvariantInfo));
        sb.Append(';');
        old_num = num + 1;
        num = IndexOfHighChar(s, old_num);
    } while (num != -1);
    sb.Append(s, old_num, s.Length - old_num);
    return sb.ToString();
}

static unsafe int IndexOfHighChar(string s, int start)
{
    int num = s.Length - start;
    fixed (char* str = s) {
        char* chPtr = str + start;
        while (num > 0) {
            char ch = chPtr[0];
            if (ch >= 'Ā')
                return s.Length - num;
            chPtr++;
            num--;
        }
    }
    return -1;
}