方法中出现错误，无法计算表达式

本文关键字：计算 表达式 错误 方法 | 更新日期: 2023-09-27 18:10:51

我得到这个错误，

无法计算表达式，因为代码已优化或本机帧位于调用堆栈的顶部。

我不知道是什么引起的。

有登录和会话选择两种方法。登录会话只匹配电子邮件和密码;会话选择用GUID查询数据库，该GUID将用作会话ID。当我在登录

中调用SessionSelection()时抛出错误
private void SessionSelection( )
{

 string connectstr = "data source=.''SQLEXPRESS;Integrated Security=True; Initial Catalog= NewApp";
    try
    {
        string query = @"SELECT UserIDkey FROM Registration WHERE Email='" + txtEmail.Text.Trim() + "'";
        SqlConnection con = new SqlConnection(connectstr);
        SqlCommand cmd = new SqlCommand(query, con);
        con.Open();
        SqlDataReader reader = cmd.ExecuteReader();
        while (reader.Read())
        {
            string SessionResult = reader["UserIDkey"].ToString();
            Session["PrivateKey"] = SessionResult;
            //SessionResult = SpecialKey;
        }
        reader.Close();
        con.Close();
    }
    catch
    {
    }
}

private void Login()
{
    string passwordEncryption = txtPassword.Text.Trim();
    System.Security.Cryptography.MD5CryptoServiceProvider x2 = new System.Security.Cryptography.MD5CryptoServiceProvider();
    byte[] bs2 = System.Text.Encoding.UTF8.GetBytes(passwordEncryption);
    bs2 = x2.ComputeHash(bs2);
    System.Text.StringBuilder s2 = new System.Text.StringBuilder();
    foreach (byte b in bs2)
    {
        s2.Append(b.ToString("x2").ToLower());
    }
    string EncryptedPassword = s2.ToString();

    if (!string.IsNullOrEmpty(txtEmail.Text))
    {
        string connectstr = "data source=.''SQLEXPRESS;Integrated Security=True; Initial Catalog= NewApp";
        //  (ConfigurationManager.AppSettings["connectionString"]); 
        try
        {
            string query = @"SELECT * FROM Registration WHERE Email='" + txtEmail.Text.Trim() + "'and Password='" + EncryptedPassword + "'";
            SqlConnection con = new SqlConnection(connectstr);
            SqlCommand cmd = new SqlCommand(query, con);
            con.Open();
            var Results = (int)cmd.ExecuteScalar();
            //string sqlRead = cmd.ExecuteReader().ToString();
            if (Results > 0)
            {

                SessionSelection();
                txtEmail.Text = "";
                txtPassword.Text = "";
                Response.Redirect("~/Home.aspx");
            }
            else
            {
                Response.Write("Incorrect UserName/Password");
            }
            con.Close();
        }

        catch (Exception ex)
        {
            Response.Write("Incorrect UserName/Password");
        }
    }

方法中出现错误，无法计算表达式

问题:您没有在Login()方法的命令字符串中给出Email string和and关键字之间的空间:

string query = @"SELECT * FROM Registration WHERE Email= 
         '" + txtEmail.Text.Trim() + "'and Password='" + EncryptedPassword + "'";
                                      ^^^

解决方案:您需要在Login()方法的命令字符串中Email string和and关键字之间有空间:

试试这个:

string query = @"SELECT * FROM Registration WHERE Email= 
      '" + txtEmail.Text.Trim() + "' and Password='" + EncryptedPassword + "'";

建议:您的查询是对SQL Injection attacks开放的，所以我强烈建议您使用Parameterised queries来避免使用SQL Injection attacks。

方案二:与Parameterised queries 

try
{
    string query = @"SELECT * FROM Registration WHERE Email=@Email 
                                                        and Password=@Password";
    SqlConnection con = new SqlConnection(connectstr);
    SqlCommand cmd = new SqlCommand(query, con);
    cmd.Parameters.AddWithValue("@Email",txtEmail.Text.Trim());
    cmd.Parameters.AddWithValue("@Password",EncryptedPassword);
    con.Open();
    var Results = (int)cmd.ExecuteScalar();
    //string sqlRead = cmd.ExecuteReader().ToString();
    if (Results > 0)
    {
        SessionSelection();
        txtEmail.Text = "";
        txtPassword.Text = "";
        Response.Redirect("~/Home.aspx");
    }
    else
    {
        Response.Write("Incorrect UserName/Password");
    }
    con.Close();
}

问题是Response.Redirect("~/Home. redirect ")。aspx",假);

要解决这个问题，可以使用以下方法之一:为响应。最后，调用HttpContext.Current.ApplicationInstance.CompleteRequest方法而不是Response。结束绕过代码执行到Application_EndRequest事件。为响应。重定向，使用重载，响应。重定向(String url, bool endResponse)，为endResponse参数传递false以抑制内部调用Response.End。例如:响应。重定向("全心全意。aspx",假);

如果您使用此解决方法，则响应之后的代码。执行重定向。为服务器。传输，使用服务器。

修复Response.Redirect("~/回家。aspx",假);

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