建立在C＃中的SQL连接 [英] Creating a sql connection in c#

问题描述

我是新来的这个网站，也编程。我是通过销售点目前正在创建的库存系统。它采用模态和非模态形式。我的问题是寿，我的工作对更改密码对话框，必须连接到数据库，以覆盖密码字段。我使用的数据库是Microsoft SQL Server管理工作室EX preSS。以下是我迄今为止必要的注释。请注意，设计的形式，我有这一定到数据库的组合框。我哪里做错了？

 私人无效ChangePwdButton_Click（对象发件人，EventArgs的）
{
  SqlConnection的sqlconn =新的SqlConnection（）;
  sqlconn.ConnectionString = @数据源= \ SQLEX $ P $干燥综合征; AttachDbFilename = C：\用户\ Gerald-院长马丁\文档\ SQL Server Management Studio中前preSS \项目\ BodyMates.mdf;集成安全性=真;用户实例=真;
     sqlconn.Open（）;
    字符串OLDPWD = txtOldPwd.Text;
    字符串NEWPWD = txtNewPwd.Text;
    字符串confirmNewPwd = txtConfirmNewPwd.Text;
    字符串sqlquery的=UPDATE [雇员] SET PWD = @ newpass，其中职工code = @ EMP code;
    的SqlCommand CMD =新的SqlCommand（sqlquery的，sqlconn）;
    cmd.Parameters.AddWithValue（@ newpass，txtConfirmNewPwd.Text）;
    cmd.Parameters.AddWithValue（@ EMP code，comboEmp code.SelectedValue）;
    //cmd.Parameters.AddWithValue("@pwd，txtNewPwd.Text）;
    cmd.Connection = sqlconn;
    cmd.ExecuteNonQuery（）;
    SqlDataReader的博士= cmd.ExecuteReader（）;
    而（dr.Read（））
    {
        如果（txtOldPwd.Text ==博士[PWD]的ToString（）及。及（txtNewPwd.Text == txtConfirmNewPwd.Text））
        {
            如果（comboEmp code.SelectedIndex == 0）
            {
               查询字符串=UPDATE [雇员] SET PWD ='+ txtConfirmNewPwd.Text +';
            }
        }

       //如果（。（txtNewPwd.Text ==博士[NEWPWD]的ToString（））及（txtConfirmNewPwd.Text ==（DR [confirmNewPwd]的ToString（））））{}
    }
   //的MessageBox.show（密码更改成功！，更改密码，MessageBoxButtons.OK，MessageBoxIcon.Information）;
}
 

解决方案

您可以使用的 的ExecuteNonQuery 像 cmd.ExecuteNonQuery（）; ，返回 INT 值。使用像这样;

  INT I = cmd.ExecuteNonQuery（）;
 

和也 的ExecuteReader（） 是这样工作的;

  SqlDataReader的读卡器= Command.ExecuteReader却（）;
        而（reader.Read（））
        {
            Console.WriteLine（的String.Format（{0}，读者[0]））;
        }
 

您可以读取返回数据的列。就像第一列阅读[0] ，第二列阅读器[1] 等

但在所有这些信息，如果你是新的节目，你可以找到很多的书建议，并在＃1有趣的信息。检查这些物品;

• <一个href="http://stackoverflow.com/questions/1711/what-is-the-single-most-influential-book-every-programmer-should-read">What是最有影响力的书每个程序员都应该阅读？
• 什么是最好的C＃的书？
• 最好的书一个新的数据库开发

I'm new to this site and also to programming. I am currently creating an inventory system via a point of sale. It uses modal and non-modal forms. My problem is tho, I'm working on the change password dialog which has to be connected to the database in order to overwrite the password field. The database i used is microsoft sql server management studio express. Here is what I have so far with the necessary comments. Please note that on the 'design' form, I have a combobox which is bounded to the database. Where did I go wrong?

private void ChangePwdButton_Click(object sender, EventArgs e)
{
  SqlConnection sqlconn = new SqlConnection();
  sqlconn.ConnectionString = @"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\Gerald-   dean Martin\Documents\SQL Server Management Studio Express\Projects\BodyMates.mdf;Integrated Security=True;User Instance=True";
     sqlconn.Open();
    string oldpwd = txtOldPwd.Text;
    string newpwd = txtNewPwd.Text;
    string confirmNewPwd = txtConfirmNewPwd.Text;
    string sqlquery = "UPDATE [Employee] SET Pwd=@newpass where EmployeeCode=@empcode";
    SqlCommand cmd = new SqlCommand(sqlquery, sqlconn);
    cmd.Parameters.AddWithValue("@newpass", txtConfirmNewPwd.Text);
    cmd.Parameters.AddWithValue("@empcode", comboEmpCode.SelectedValue);
    //cmd.Parameters.AddWithValue("@pwd", txtNewPwd.Text);
    cmd.Connection = sqlconn;
    cmd.ExecuteNonQuery();
    SqlDataReader dr = cmd.ExecuteReader();             
    while (dr.Read())
    {
        if(txtOldPwd.Text == dr["pwd"].ToString() && (txtNewPwd.Text == txtConfirmNewPwd.Text))
        {
            if (comboEmpCode.SelectedIndex == 0)
            {
               string query = "UPDATE [Employee] SET Pwd = '" + txtConfirmNewPwd.Text + "'";
            }
        }

       // if ((txtNewPwd.Text == dr["newpwd"].ToString()) & (txtConfirmNewPwd.Text == (dr["confirmNewPwd"].ToString()))) { }
    }
   // MessageBox.Show("Password was changed Successfully!", "Password Change", MessageBoxButtons.OK, MessageBoxIcon.Information); 
}

解决方案

You can use ExecuteNonQuery like cmd.ExecuteNonQuery(); It returns int value. Use it like this;

int i = cmd.ExecuteNonQuery();

And also ExecuteReader() works like this;

SqlDataReader reader = command.ExecuteReader();
        while (reader.Read())
        {
            Console.WriteLine(String.Format("{0}", reader[0]));
        }

You can read returning data's column. Like first column reader[0], second column reader[1] etc.

But before all this information, if you are new to programming, you can find a lot of book proposal and useful informations on Stackoverflow. Check these articles;

• What is the single most influential book every programmer should read?
• What are the best C# books?
• Best Book for a new Database Developer

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