c#函数返回的一个问题。望各位前辈指教

[yilutage]

错误 1 “robot.PostDate.LogIN(string, string, string)”: 并非所有的代码路径都返回值 F:\c#\robot\robot\PostDate.cs 10 30 robot


请问这个错误怎么解决。我是新手，刚接触c#还望各位多多指点！
public static string LogIN(string URI, string email, string password)
{
try
{
CookieContainer cookieContainer = new CookieContainer();

///////////////////////////////////////////////////
// 1.打开 MyLogin.aspx 页面，获得 GetVeiwState & EventValidation
///////////////////////////////////////////////////
// 设置打开页面的参数
// string URI = "http://login.xiaonei.com/Login.do";
HttpWebRequest request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "GET";
request.KeepAlive = true;

// 接收返回的页面
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
System.IO.Stream responseStream = response.GetResponseStream();
System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
string srcString = reader.ReadToEnd();

// 获取页面的 VeiwState
string viewStateFlag = "id=\"__VIEWSTATE\" value=\"";
int i = srcString.IndexOf(viewStateFlag) + viewStateFlag.Length;
int j = srcString.IndexOf("\"", i);
string viewState = srcString.Substring(i, j - i);

// 获取页面的 EventValidation
string eventValidationFlag = "id=\"__EVENTVALIDATION\" value=\"";
i = srcString.IndexOf(eventValidationFlag) + eventValidationFlag.Length;
j = srcString.IndexOf("\"", i);
string eventValidation = srcString.Substring(i, j - i);

///////////////////////////////////////////////////
// 2.自动填充并提交 MyLogin.aspx 页面
///////////////////////////////////////////////////
// 提交按钮的文本
string submitButton = "登录";

// 将文本转换成 URL 编码字符串
// viewState = System.Web.HttpUtility.UrlEncode(viewState);
// eventValidation = System.Web.HttpUtility.UrlEncode(eventValidation);
// submitButton = System.Web.HttpUtility.UrlEncode(submitButton);

// 要提交的字符串数据。格式形如:user=uesr1&password=123
string formatString = "email={0}&password={1}&origURL=http%3A%2F%2Fwww.xiaonei.com%2FSysHome.do";
string postString = string.Format(formatString, email, password, submitButton, viewState, eventValidation);

// 将提交的字符串数据转换成字节数组
byte[] postData = Encoding.ASCII.GetBytes(postString);

// 设置提交的相关参数
request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "POST";
request.KeepAlive = true;
request.ContentType = "application/x-www-form-urlencoded";
request.CookieContainer = cookieContainer;
request.ContentLength = postData.Length;

// 提交请求数据
System.IO.Stream outputStream = request.GetRequestStream();
outputStream.Write(postData, 0, postData.Length);
outputStream.Close();

// 接收返回的页面
response = request.GetResponse() as HttpWebResponse;
responseStream = response.GetResponseStream();
reader = new System.IO.StreamReader(responseStream, Encoding.GetEncoding("GB2312"));
srcString = reader.ReadToEnd();

///////////////////////////////////////////////////
// 3.打开 Default.aspx 页面
///////////////////////////////////////////////////
// 设置打开页面的参数

URI = "http://apps.xiaonei.com/happyfarm";

request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "GET";
request.KeepAlive = true;
request.CookieContainer = cookieContainer;

// 接收返回的页面
response = request.GetResponse() as HttpWebResponse;
responseStream = response.GetResponseStream();
reader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
srcString = reader.ReadToEnd();
return srcString;
///////////////////////////////////////////////////
// 4.分析返回的页面
///////////////////////////////////////////////////
// ...... ......

}
catch (WebException we)
{
string msg = we.Message;
}

[xlievo]

异常 的返回值在哪？

[IamHandsomeman]

[Quote=引用 5 楼 xlievo 的回复:]
异常 的返回值在哪？
[/Quote]
UP

[jdbcodbc]

你return个返回值呗

[路人乙e]

catch (WebException we)
{
string msg = we.Message;
return msg;
}

[moonshineidolon]

public static string LogIN(string URI, string email, string password)
{
string srcString=String.Empty;

try
{
CookieContainer cookieContainer = new CookieContainer();

///////////////////////////////////////////////////
// 1.打开 MyLogin.aspx 页面，获得 GetVeiwState & EventValidation
///////////////////////////////////////////////////
// 设置打开页面的参数
// string URI = "http://login.xiaonei.com/Login.do";
HttpWebRequest request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "GET";
request.KeepAlive = true;

// 接收返回的页面
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
System.IO.Stream responseStream = response.GetResponseStream();
System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
srcString = reader.ReadToEnd();

// 获取页面的 VeiwState
string viewStateFlag = "id=\"__VIEWSTATE\" value=\"";
int i = srcString.IndexOf(viewStateFlag) + viewStateFlag.Length;
int j = srcString.IndexOf("\"", i);
string viewState = srcString.Substring(i, j - i);

// 获取页面的 EventValidation
string eventValidationFlag = "id=\"__EVENTVALIDATION\" value=\"";
i = srcString.IndexOf(eventValidationFlag) + eventValidationFlag.Length;
j = srcString.IndexOf("\"", i);
string eventValidation = srcString.Substring(i, j - i);

///////////////////////////////////////////////////
// 2.自动填充并提交 MyLogin.aspx 页面
///////////////////////////////////////////////////
// 提交按钮的文本
string submitButton = "登录";

// 将文本转换成 URL 编码字符串
// viewState = System.Web.HttpUtility.UrlEncode(viewState);
// eventValidation = System.Web.HttpUtility.UrlEncode(eventValidation);
// submitButton = System.Web.HttpUtility.UrlEncode(submitButton);

// 要提交的字符串数据。格式形如:user=uesr1&password=123
string formatString = "email={0}&password={1}&origURL=http%3A%2F%2Fwww.xiaonei.com%2FSysHome.do";
string postString = string.Format(formatString, email, password, submitButton, viewState, eventValidation);

// 将提交的字符串数据转换成字节数组
byte[] postData = Encoding.ASCII.GetBytes(postString);

// 设置提交的相关参数
request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "POST";
request.KeepAlive = true;
request.ContentType = "application/x-www-form-urlencoded";
request.CookieContainer = cookieContainer;
request.ContentLength = postData.Length;

// 提交请求数据
System.IO.Stream outputStream = request.GetRequestStream();
outputStream.Write(postData, 0, postData.Length);
outputStream.Close();

// 接收返回的页面
response = request.GetResponse() as HttpWebResponse;
responseStream = response.GetResponseStream();
reader = new System.IO.StreamReader(responseStream, Encoding.GetEncoding("GB2312"));
srcString = reader.ReadToEnd();

///////////////////////////////////////////////////
// 3.打开 Default.aspx 页面
///////////////////////////////////////////////////
// 设置打开页面的参数

URI = "http://apps.xiaonei.com/happyfarm";

request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "GET";
request.KeepAlive = true;
request.CookieContainer = cookieContainer;

// 接收返回的页面
response = request.GetResponse() as HttpWebResponse;
responseStream = response.GetResponseStream();
reader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
srcString = reader.ReadToEnd();

///////////////////////////////////////////////////
// 4.分析返回的页面
///////////////////////////////////////////////////
// ...... ......

}
catch (WebException we)
{
string msg = we.Message;
}
return srcString;
}

[PandaIT]

return "";

public static string LogIN

你这里设置有返回值！

[冰凝瞬间1986]

catch (WebException we)
{
string msg = we.Message;
return "";
}
还有就是srcString的作用域写在TRY块外面也可以，函数返回值必须是在函数域里面才可以...

[yangqidong]

函数在任何代码执行路径都必须要有返回值

[gciyfzx07]

初步看到异常那没返回值

[zhoulehua]

//你的函数一定要有返回值的
try
{
    ......
    return 
}
catch
{
    //或者return
    //或者抛出异常
}

[冷月孤峰]

异常里没有返回值：
catch (WebException we)
{
string msg = we.Message;
}
改成：
catch (WebException we)
{
return we.Message;
}

[cja03]

如果发生异常，会进去catch
而执行了catch后，没有写这个方法的返回值。

[shenjq]

www.xmcoa.com

[cja03]

你可以参考TryParse的作法：

public static bool LogIN(string URI, string email, string password, out str)
{
try
{
....
str=
return true;
}
catch(WebException we)
{
str=we.Message;
return false
}
}

如果返回true，说明登陆成功，而str就是你要的东西
如果返回false，说明登陆失败，str记录着失败（异常）的原因

[我姓区不姓区]

在catch里加
return "";