C# 全角符号转半角

public static string SBCCaseToNumberic(string SBCCase)
{
char[] c = SBCCase.ToCharArray();
for (int i = 0; i < c.Length; i++)
{
byte[] b = System.Text.Encoding.Unicode.GetBytes(c, i, 1);
if (b.Length == 2)
{
if (b[1] == 255)
{
b[0] = (byte)(b[0] + 32);
b[1] = 0;
c[i] = System.Text.Encoding.Unicode.GetChars(b)[0];
}
}
}
return new string(c);
}