C#大小写字母转换，不能调用ToUpper，ToLower函数，

---

//小写升薯转薯脊大写
static string LowerToUpper(string in_str)
{
int i;
string str;
char[] ch;
ch = in_str.ToCharArray();

for (i = 0; i < in_str.Length; i++)
{

if (ch[i] >= 'a' && ch[i] <= 'z')
{
ch[i] =Convert.ToChar( 'A' + (ch[i] - 'a'));
}

}
str = new string(ch);
return str;
}

//大数笑渗写转小写
static string UpperToLower(string in_str)
{
int i;
string str;
char[] ch;
ch = in_str.ToCharArray();

for (i = 0; i < in_str.Length; i++)
{

if (ch[i] >= 'A' && ch[i] <= 'Z')
{
ch[i] = Convert.ToChar('a' + (ch[i] - 'A'));
}

}
str = new string(ch);
return str;
}

---

你要导入text包的哈

---