string s = textBox1.Text;
byte[] b = UnicodeEncoding.Default.GetBytes(s);
char[] c = UnicodeEncoding.Default.GetChars(b, 0, b.Length);
string s1 = textBox2.Text;
byte[] b1 = UnicodeEncoding.Default.GetBytes(s);
char[] c1 = UnicodeEncoding.Default.GetChars(b, 0, b.Length);
textBox3.Text = cCdll.strA(C,C1);
byte[] b = UnicodeEncoding.Default.GetBytes(s);
char[] c = UnicodeEncoding.Default.GetChars(b, 0, b.Length);
string s1 = textBox2.Text;
byte[] b1 = UnicodeEncoding.Default.GetBytes(s);
char[] c1 = UnicodeEncoding.Default.GetChars(b, 0, b.Length);
textBox3.Text = cCdll.strA(C,C1);
public static extern IntPtr strA(IntPtr a, IntPtr b);
改这样吧,C#的char貌似不是单字节的
IntPtr a=Marshal.StringToBSTR(textBox1.Text);
IntPtr b=Marshal.StringToBSTR(textBox2.Text);
IntPtr d=strA(a,b);
TextBox3.Text=Marshal.PtrToStringAuto(d);
试试看