Asp.net write login verification code

Login. aspx. cs File

1. Using System. Drawing;
2. Using System. Drawing. Imaging;
3. Private void Page_Load (object sender, System. EventArgs e)
4. {
5. // Place user code here to initialize the page
6. // RndNum is a user-defined function.
7. String VNum = RndNum (4); // here the number 4 represents a 4-digit verification string!
8. Session ["VNum"] = VNum;
9. ValidateCode (VNum );
10. }
11. // Image generation function
12. Private void ValidateCode (string VNum)
13. {
14. Int Gheight = (int) (VNum. Length * 11.5 );
15. // Gheight indicates the image width. The image width is automatically changed based on the Character length.
16. System. Drawing. Bitmap Img = new System. Drawing. Bitmap (Gheight, 20 );
17. Graphics g = Graphics. FromImage (Img );
18. G. DrawString (VNum, new System. Drawing. Font ("Arial", 10), new System. Drawing. SolidBrush (Color. Red), 3,3 );
19. // Draw a string in the rectangle (string, Font, paint color, top left x. Top left y)
20. System. IO. MemoryStream MS = new System. IO. MemoryStream ();
21. Img. Save (MS, System. Drawing. Imaging. ImageFormat. Png );
22. Response. ClearContent (); // You Need to output the image information to modify the HTTP header.
23. Response. ContentType = "image/Png ";
24. Response. BinaryWrite (ms. ToArray ());
25. G. Dispose ();
26. Img. Dispose ();
27. Response. End ();
28. }
30. // The random number generation function is randomly extracted from the Vchar array.
31. // Uppercase/lowercase letters
32. Public string RndNum (int VcodeNum)
33. {
34. String Vchar = ", A, B, C, D, E, F, G, H, I, J, K, L, M, n, O, P, Q, R, S, T, U, W, X, Y, Z ";
36. String [] VcArray = Vchar. Split (,);
37. String VNum = ""; // StringBuilder is not required because the string is short.
38. Int temp =-1; // record the previous random value. Avoid producing several identical random numbers.
40. // Use a simple algorithm to ensure different random numbers are generated
41. Random rand = new Random ();
42. For (int I = 1; I <VcodeNum 1; I)
43. {
44. If (temp! =-1)
45. {
46. Rand = new Random (I * temp * unchecked (int) DateTime. Now. Ticks ));
47. }
48. // Int t = rand. Next (35 );
49. Int t = rand. Next (35 );
50. If (temp! =-1 & temp = t)
51. {
52. Return RndNum (VcodeNum );
53. }
54. Temp = t;
55. VNum = VcArray [t];
57. }
58. Return VNum;
59. }
60. Public void doit (object sender, System. EventArgs e)
61. {
62. If (Page. IsValid)
63. {
65. String VNum;
66. VNum = Session ["VNum"]. ToString ();
67. ViewState ["VNum"] = VNum;
68. If (this. Vcode. Text = ViewState ["VNum"]. ToString ())
69. {
71. Hover. Manage. CheckLogin obj = new Hover. Manage. CheckLogin ();
72. String name = username. Text;
73. String password = FormsAuthentication. HashPasswordForStoringInConfigFile (pass. Text. ToString (), "md5 ");
74. If (! Obj. checklogin (name, password ))
75. {
76. Response. Redirect (".../Error. aspx? Action = Errorlogin ");
77. Response. End ();
78. Return;
79. }
80. Else
81. {
82. Session. Add ("adminname", name );
83. Session. Add ("adminpass", password );
84. Response. Redirect ("Default. aspx ");
85. Response. End ();
86. Return;
87. }
89. }
90. Else
91. {
92. Response. Write ("<script> alert (" enter the correct additional code! "); </Script> ");
93. }
94. }
95. }
96. // Verify if the submitted verification string is correct!
97. // Otherwise, the system prompts you to return to the logon page! You can also simplify this page!
98. If (this. Vcode. Text = ViewState ["VNum"]. ToString ())
99. {
100. Response. Write ("correct Verification Code ");
101. }
102. Else
103. {
104. Response. Write ("Verification code error! ");
105. }
108. The following is the response event of Login. Aspx in which the submit button is called.
109. Public void doit (object sender, System. EventArgs e)
110. {
111. If (Page. IsValid)
112. {
114. String VNum;
115. VNum = Session ["VNum"]. ToString ();
116. ViewState ["VNum"] = VNum;
117. If (this. Vcode. Text = ViewState ["VNum"]. ToString ())
118. {
120. Hover. Manage. CheckLogin obj = new Hover. Manage. CheckLogin ();
121. String name = username. Text;
122. String password = FormsAuthentication. HashPasswordForStoringInConfigFile (pass. Text. ToString (), "md5 ");
123. If (! Obj. checklogin (name, password ))
124. {
125. Response. Redirect (".../Error. aspx? Action = Errorlogin ");
126. Response. End ();
127. Return;
128. }
129. Else
130. {
131. Session. Add ("adminname", name );
132. Session. Add ("adminpass", password );
133. Response. Redirect ("Default. aspx ");
134. Response. End ();
135. Return;
136. }
138. }
139. Else
140. {
141. Response. Write ("<script> alert (" enter the correct additional code! "); </Script> ");
142. }
143. }
144. }
145. If the verification string submitted is correct, verify that it is a legal user!
146. Otherwise, the system prompts you to return to the logon page! You can also simplify this page!
147. If (this. Vcode. Text = ViewState ["VNum"]. ToString ())
148. {
149. Response. Write ("correct Verification Code ");
150. }
151. Else
152. {
153. Response. Write ("Verification code error! ");
154. }