字符串引用未设置为字符串实例
我正在使用此Topaz签名板，并尝试将其保存到数据库中。现在，我有一个输入字段，可以在文本框（HTML）中获取用户名，如下所示：
<input type="text" name="username" id="username" />
现在，当我像这样在后面的代码中调用它时
protected void Page_Load(object sender, EventArgs e)
{
//Put user code to initialize the page here
Topaz.SigPlusNET sigObj = new Topaz.SigPlusNET();
sigObj.AutoKeyStart();
//use the same data to decrypt signature
sigObj.SetAutoKeyData(Request.Form["username"]); <--- Error shows here
sigObj.AutoKeyFinish();
sigObj.SetSigCompressionMode(1);
sigObj.SetEncryptionMode(2);
//Now, get sigstring from client
//Sigstring can be stored in a database if
//a biometric signature is desired rather than an image
sigObj.SetSigString(Request.Form["hidden"]);
if (sigObj.NumberOfTabletPoints() > 0)
{
sigObj.SetImageFileFormat(0);
sigObj.SetImageXSize(500);
sigObj.SetImageYSize(150);
sigObj.SetImagePenWidth(8);
sigObj.SetJustifyX(5);
sigObj.SetJustifyY(5);
sigObj.SetJustifyMode(5);
System.Drawing.Image img = sigObj.GetSigImage();
base64ImageString = ImageToBase64(img, System.Drawing.Imaging.ImageFormat.Jpeg);
/* String path;
//path = System.AppDomain.CurrentDomain.BaseDirectory & "mySig.bmp"
path = "C:\\mySig.bmp";
img.Save(path, System.Drawing.Imaging.ImageFormat.Bmp);
Response.Write("Image saved successfully to " + path);
*/
//Send to database
if (sigBase64.Length > 3000)
{
using (SqlConnection con = new SqlConnection(constring))
{
con.Open();
string sql = "insert into SakalPicturecontrol (firstname,lastname,email,base64ImageString) Values (@firstname,@lastname,@email,@base64ImageString)";
try
{
using (SqlCommand cmd = new SqlCommand(sql, con))
{
cmd.Parameters.AddWithValue("@firstname", firstname);
cmd.Parameters.AddWithValue("@lastname", lastname);
cmd.Parameters.AddWithValue("@email", email);
cmd.Parameters.AddWithValue("@base64ImageString", base64ImageString);
cmd.ExecuteNonQuery();
Response.Write("Information has been saved Correctly..");
con.Close();
}
}
catch (Exception ex)
{
Response.Write("Error: " + ex.ToString());
}
}
}
}
else
{
//signature has not been returned successfully!
}
}
我收到此错误，String Reference not set to instance of String。我想念什么吗？我可能无法正确执行某些操作吗？
修改
当我执行Shift + F9组合键时，我会得到这张图片
修改
HTML部分如下所示：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="SignatureCaptureForm.aspx.cs" Inherits="SakalGBSignatureProcess.SignatureCaptureForm" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style type="text/css">
.auto-style1 {
width: 20px;
}
.auto-style4 {
left: 0px;
width: 424px;
top: 0px;
height: 204px;
}
.auto-style5 {
width: 344px;
}
.auto-style6 {
width: 509px;
text-align: right;
}
.auto-style7 {
width: 90%;
}
.auto-style8 {
width: 328px;
}
.auto-style10 {
width: 317px;
}
</style>
<script type="javascript">
function OnClear()
{
document.TopazForm.SigPlus1.ClearTablet(); //Clears the signature, in case of error or mistake
}
function onSign()
{
document.TopazForm.SigPlus1.TabletState = 1;
}
function onSave()
{
if(document.TopazForm.username.value == "")
{
alert("Please Username Before Continuing...");
return false;
}
if(document.TopazForm.SigPlus1.NumberOfTabletPoints > 0)
{
document.TopazForm.SigPlus1.TabletState = 0; //Turns tablet off
document.TopazForm.SigPlus1.AutoKeyStart();
document.TopazForm.SigPlus1.AutoKeyData = document.TopazForm.username.value;
//pass here the data you want to use to encrypt the signature
//this demo simply encrypts to the name typed in by the user
//you'll probably want to make sure your encryption data you use is
//more useful...that you encrypt the signature to the data important
//to your app, and what the client has agreed to
document.TopazForm.SigPlus1.AutoKeyFinish();
document.TopazForm.SigPlus1.EncryptionMode = 2;
document.TopazForm.SigPlus1.SigCompressionMode = 1;
document.TopazForm.hidden.value = document.TopazForm.SigPlus1.SigString;
//pass the signature ASCII hex string to the hidden field,
//so it will be automatically passed when the page is submitted
document.TopazForm.submit();
}
else
{
alert("Please Sign Before Continuing...");
return false;
}
}
</script>
</head>
<body>
<form id="TopazForm" name="TopazForm" method="post" action="SignatureCaptureForm.aspx" />
<div>
<table class="auto-style7">
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020"> </td>
<td class="auto-style1"> </td>
<td>
</td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020">Username: </td>
<td class="auto-style1"> </td>
<td>
<INPUT id="username" type="text" name="username" class="auto-style8"></td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020">First Name : </td>
<td class="auto-style1"> </td>
<td>
<input id="firstname" class="auto-style8" type="text" name="firstname" runat="server"/></td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020">Last Name : </td>
<td class="auto-style1"> </td>
<td>
<input id="lastname" class="auto-style8" type="text" name="lastname" runat="server" /></td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020">Email: </td>
<td class="auto-style1"> </td>
<td>
<input id="email" class="auto-style8" type="text" name="email" runat="server"/></td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020">Passport Photograph:</td>
<td class="auto-style1"> </td>
<td>
<asp:Image ID="passport" runat="server" Height="164px" Width="170px" />
</td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020"> </td>
<td class="auto-style1"> </td>
<td>
<asp:FileUpload ID="FileUpload1" runat="server" />
</td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020">Signature Capture:</td>
<td class="auto-style1"> </td>
<td><OBJECT id="SigPlus1"
classid="clsid:69A40DA3-4D42-11D0-86B0-0000C025864A" name="SigPlus1" class="auto-style4">
<PARAM NAME="_Version" VALUE="131095">
<PARAM NAME="_ExtentX" VALUE="11218">
<PARAM NAME="_ExtentY" VALUE="5398">
<PARAM NAME="_StockProps" VALUE="9">
</OBJECT></td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020"> </td>
<td class="auto-style1"> </td>
<td> </td>
</tr>
<tr>
<td class="auto-style6" style="font-family: 'Century Gothic'; font-size: medium; font-weight: normal; font-style: normal; color: #202020"> </td>
<td class="auto-style1"> </td>
<td>
<table style="width:100%;">
<tr>
<td class="auto-style5">
<input id="SignBtn" type="button" value="Sign" onclick="onSign();"/>
<input id="ClearBtn" type="button" value="Clear" onclick="OnClear();" /></td>
<td>
<input id="Button1" type="button" value="Save" onclick="onSave();" />
<INPUT id="hidden" type="hidden" name="hidden"></td>
</tr>
</table>
</td>
</tr>
</table>
</div>
</form>
</body>
</html>
和后端（后面的代码）看起来像这样
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data.SqlClient;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.Configuration;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace SakalGBSignatureProcess
{
public partial class SignatureCaptureForm : System.Web.UI.Page
{
string base64ImageString;
string constring = WebConfigurationManager.ConnectionStrings["MYCON"].ConnectionString;
protected void Page_Load(object sender, EventArgs e)
{
//Put user code to initialize the page here
Topaz.SigPlusNET sigObj = new Topaz.SigPlusNET();
sigObj.AutoKeyStart();
//use the same data to decrypt signature
sigObj.SetAutoKeyData(Request.Form["username"]);
sigObj.AutoKeyFinish();
sigObj.SetSigCompressionMode(1);
sigObj.SetEncryptionMode(2);
//Now, get sigstring from client
//Sigstring can be stored in a database if
//a biometric signature is desired rather than an image
sigObj.SetSigString(Request.Form["hidden"]);
if (sigObj.NumberOfTabletPoints() > 0)
{
sigObj.SetImageFileFormat(0);
sigObj.SetImageXSize(500);
sigObj.SetImageYSize(150);
sigObj.SetImagePenWidth(8);
sigObj.SetJustifyX(5);
sigObj.SetJustifyY(5);
sigObj.SetJustifyMode(5);
System.Drawing.Image img = sigObj.GetSigImage();
base64ImageString = ImageToBase64(img, System.Drawing.Imaging.ImageFormat.Jpeg);
/* String path;
//path = System.AppDomain.CurrentDomain.BaseDirectory & "mySig.bmp"
path = "C:\\mySig.bmp";
img.Save(path, System.Drawing.Imaging.ImageFormat.Bmp);
Response.Write("Image saved successfully to " + path);
*/
//Send to database
if (base64ImageString.Length > 3000)
{
using (SqlConnection con = new SqlConnection(constring))
{
con.Open();
string sql = "insert into SakalPicturecontrol (firstname,lastname,email,base64ImageString) Values (@firstname,@lastname,@email,@base64ImageString)";
try
{
using (SqlCommand cmd = new SqlCommand(sql, con))
{
cmd.Parameters.AddWithValue("@firstname", firstname);
cmd.Parameters.AddWithValue("@lastname", lastname);
cmd.Parameters.AddWithValue("@email", email);
cmd.Parameters.AddWithValue("@base64ImageString", base64ImageString);
cmd.ExecuteNonQuery();
Response.Write("Information has been saved Correctly..");
con.Close();
}
}
catch (Exception ex)
{
Response.Write("Error: " + ex.ToString());
}
}
}
}
else
{
//signature has not been returned successfully!
}
}
/* protected void Button2_Click(object sender, EventArgs e)
{
}*/
public string ImageToBase64(System.Drawing.Image image, System.Drawing.Imaging.ImageFormat format)
{
using (MemoryStream ms = new MemoryStream())
{
// Convert Image to byte[]
image.Save(ms, format);
byte[] imageBytes = ms.ToArray();
// Convert byte[] to Base64 String
string base64String = Convert.ToBase64String(imageBytes);
return base64String;
}
}
/* protected void Button3_Click(object sender, EventArgs e)
{
}*/
}
}
1 个答案:
答案 0 :(得分：0)
您需要在html中将文本框的名称设置为用户名，或者需要在此行中使用正确的名称：
sigObj.SetAutoKeyData(Request.Form["username"]);
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