我该如何处理错误 [英] How do I handle the error

问题描述

当我运行我的程序时出现此错误SQLException未处理。消息=建立与SQL Server的连接时发生与网络相关或特定于实例的错误。未找到服务器或无法访问服务器。验证实例名称是正确的，并且SQL Server配置为允许远程连接。（提供程序：命名管道提供程序，错误：40 - 无法打开与SQL Server的连接）我的程序是这样的。

when i run my program this error comes" SQLException was unhandled. Message=A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)" My program is like this.

private void buttonlogin_Click(object sender, EventArgs e)
        {
            SqlDataAdapter sda = new SqlDataAdapter("Select * From Profile_Master Where pro_user_id='" + usernametextBox.Text + "' and pro_password ='" + passwordtextBox.Text + "' ", con );
            DataTable dt = new DataTable();
            sda.Fill(dt);
            if (dt.Rows.Count == 1)
            {
                LMS obj = new LMS();
                obj.Show();
                this.Hide();
            }
            else
            {
                MessageBox.Show("Invalid User Name or Password","Alert", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

我的尝试：



i google但我找不到任何解决方案。

What I have tried:

i google it but i can't find any solution.

推荐答案

你注意到的问题可能仍然是你的连接字符串：如何连接数据库C＃项目。 [ ^ ]但是请不要不这样做！



1）永远不要连接字符串来构建SQL命令。它让您对意外或故意的SQL注入攻击持开放态度，这可能会破坏您的整个数据库。总是使用参数化查询。



连接字符串时会导致问题，因为SQL会收到如下命令：

The problem you have noticed is probably still your connection string: How do I connect database C# project.[^] but don't do it like that!

1) Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

就SQL而言，用户添加的引号会终止字符串，并且您会遇到问题。但情况可能更糟。如果我来并改为输入：x'; DROP TABLE MyTable; - 然后SQL收到一个非常不同的命令：

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

哪个SQL看作三个单独的命令：

Which SQL sees as three separate commands:

SELECT * FROM MyTable WHERE StreetAddress = 'x';

完全有效的SELECT

A perfectly valid SELECT

DROP TABLE MyTable;

完全有效的删除表格通讯和

A perfectly valid "delete the table" command

--'

其他一切都是评论。

所以它确实：选择任何匹配的行，从数据库中删除表，并忽略其他任何内容。



所以总是使用参数化查询！或者准备好经常从备份中恢复数据库。您是否定期进行备份，不是吗？



2）切勿以明文形式存储密码 - 这是一个主要的安全风险。有关如何在此处执行此操作的信息：密码存储：如何做到这一点。 [ ^ ]

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

2) Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^]

SqlDataAdapter sda = new SqlDataAdapter("Select * From Profile_Master Where pro_user_id='" + usernametextBox.Text + "' and pro_password ='" + passwordtextBox.Text + "' ", con );

没有必要解决你的问题，但你有另一个问题。

永远不要通过连接字符串来构建SQL查询。迟早，您将使用用户输入来执行此操作，这会打开一个名为SQL注入的漏洞，这对您的数据库很容易并且容易出错。

名称中的单引号你的程序崩溃。如果用户输入像Brian O'Conner这样的名称可能会使您的应用程序崩溃，那么这是一个SQL注入漏洞，崩溃是最少的问题，恶意用户输入，并且它被提升为具有所有凭据的SQL命令。

SQL注入 - 维基百科 [ ^ ]

SQL注入 [ ^ ]

按示例进行SQL注入攻击 [ ^ ]

PHP：SQL注入 - 手册 [ ^ ]

SQL注入预防备忘单 - OWASP [ ^ ]

我该怎么办？解释没有技术术语的SQL注入？ - 信息安全堆栈交换 [ ^ ]

Not necessary a solution to your question, but another problem you have.
Never build an SQL query by concatenating strings. Sooner or later, you will do it with user inputs, and this opens door to a vulnerability named "SQL injection", it is dangerous for your database and error prone.
A single quote in a name and your program crash. If a user input a name like "Brian O'Conner" can crash your app, it is an SQL injection vulnerability, and the crash is the least of the problems, a malicious user input and it is promoted to SQL commands with all credentials.
SQL injection - Wikipedia[^]
SQL Injection[^]
SQL Injection Attacks by Example[^]
PHP: SQL Injection - Manual[^]
SQL Injection Prevention Cheat Sheet - OWASP[^]
How can I explain SQL injection without technical jargon? - Information Security Stack Exchange[^]

注意，该错误信息：

Note, that error message:

Quote：

SQLException未处理。 Message =建立与SQL Server的连接时发生与网络相关或特定于实例的错误。服务器未找到或无法访问。验证实例名称是否正确，以及SQL Server是否配置为允许远程连接。 （提供者：命名管道提供者，错误：40 - 无法打开与SQL Server的连接）我的程序是这样的

SQLException was unhandled. Message=A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)" My program is like this

与之无关您发布的代码片段。它与以下内容有关：

1）sql server settings

和/或

2）连接字符串



首先，检查SQL服务器实例是否启用了远程连接。请参阅：

配置远程访问服务器配置选项 - SQL Server | Microsoft Docs [ ^ ]

解决Connectiv SQL Server的错误 [ ^ ]



您可以在此处找到正确的连接字符串：SQL Server连接字符串 - ConnectionStrings.com [ ^ ]

is NOT related to the piece of code you've posted. It's related to:
1) sql server settings
and/or
2) connection string

So, first of all, check if SQL server instance is enabling remote connections. See:
Configure the remote access Server Configuration Option - SQL Server | Microsoft Docs[^]
Solving Connectivity errors to SQL Server[^]

A proper connection string you'll find here: SQL Server connection strings - ConnectionStrings.com[^]

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