从数据库中检索值 [英] retrieve values from database

问题描述

我有一张我在vs 2008中创建的表格。我编写了一个代码来在数据库中插入值。它成功执行。但是如何编写一个代码来解释我输入的所有值或不使用seqel server 2008 r2等等。我的代码插入值如下：



< pre lang =c＃> SqlConnection connection1 = new SqlConnection（）;
SqlCommand Insert = new SqlCommand（）;
Insert.Connection = connection1;
connection1.ConnectionString =（ @ Data Source = .\SQLEXPRESS; AttachDbFilename = C：\ Users \ Acer \Documents\employeeDB.mdf; Integrated Security = True; Connect Timeout = 30; User Instance = True）;
int a = Convert.ToInt32（txtEmpId.Text）;
string b = txtEmpName.Text;
int c = Convert.ToInt32（txtSalary.Text）;
string d = txtCity.Text;
Insert.CommandText = INSERT INTO Employeetable（EmpId，EmpName，Salary，City）值（@a， @ b，@ C，@ d）;
Insert.Parameters.AddWithValue（ @ a，a）;
Insert.Parameters.AddWithValue（ @ b，b）;
Insert.Parameters.AddWithValue（ @ c，c）;
Insert.Parameters.AddWithValue（ @ d，d）;
Insert.Connection.Open（）;
Insert.ExecuteNonQuery（）;
Insert.Connection.Close（）;
Response.Write（ 您已成功插入数据）;
}。

谢谢。告诉我在VS上创建的读取按钮上写的代码。

解决方案

它非常相似，但您需要更改查询，并使用不同的功能。有两种基本方法：一种使用DataReader，另一种使用DataAdapter：

 使用（SqlConnection con =  new  SqlConnection（strConnect））
 {
 con.Open（）; 
 使用（SqlCommand com =  new  SqlCommand（   SELECT iD，description FROM myTable WHERE Id = @ID，con））
 {
 com..Parameters.AddWithValue （  @ ID，myTextBox.Text）; 
 使用（SqlDataReader reader = com.ExecuteReader（））
 {
  while （reader.Read（））
 {
  int  id =（ int ）reader [  iD]; 
  string  desc =（ string ）reader [   description]; 
 Console.WriteLine（  ID：{0} \ n {1}， iD，desc）; 
} 
} 
} 
} 

 使用（SqlConnection con =  new  SqlConnection（strConnect））
 {
 con.Open（）; 
 使用（SqlDataAdapter da =  new  SqlDataAdapter（   SELECT iD，description FROM myTable WHERE Id = @ID，con））
 {
 da.SelectCommand.Parameters。 AddWithValue（  @ ID，myTextBox.Text）; 
 DataTable dt =  new  DataTable（）; 
 da.Fill（dt）; 
 myDataGridView.DataSource = dt; 
} 
} 

I have a table that i have created in vs 2008 only. i write a code to insert values in database.And it executed succesfully. but how to write a code that dislay me all the entered values or without using seqel server 2008 r2 or so on.my code for inserting values is as follows:

SqlConnection connection1 = new SqlConnection();
      SqlCommand Insert = new SqlCommand();
      Insert.Connection = connection1;
      connection1.ConnectionString = (@"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\Acer\Documents\employeeDB.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True");
      int a = Convert.ToInt32(txtEmpId.Text);
      string b = txtEmpName.Text;
      int c = Convert.ToInt32(txtSalary.Text);
      string d = txtCity.Text;
      Insert.CommandText = "INSERT INTO Employeetable(EmpId,EmpName,Salary,City) Values (@a,@b,@c,@d)";
      Insert.Parameters.AddWithValue("@a", a);
      Insert.Parameters.AddWithValue("@b", b);
      Insert.Parameters.AddWithValue("@c", c);
      Insert.Parameters.AddWithValue("@d", d);
        Insert.Connection.Open();
      Insert.ExecuteNonQuery();
      Insert.Connection.Close();
      Response.Write("you have succesfully inserted data");
  }.

Thanks.tell me what code to write on read button that i have created on VS.

解决方案

It's very similar, but you need to change the query, and use a different function. There are two basic ways: one uses a DataReader, the other a DataAdapter:

using (SqlConnection con = new SqlConnection(strConnect))
    {
    con.Open();
    using (SqlCommand com = new SqlCommand("SELECT iD, description FROM myTable WHERE Id = @ID", con))
        {
        com..Parameters.AddWithValue("@ID", myTextBox.Text);
        using (SqlDataReader reader = com.ExecuteReader())
            {
            while (reader.Read())
                {
                int id = (int) reader["iD"];
                string desc = (string) reader["description"];
                Console.WriteLine("ID: {0}\n    {1}", iD, desc);
                }
            }
        }
    }

using (SqlConnection con = new SqlConnection(strConnect))
    {
    con.Open();
    using (SqlDataAdapter da = new SqlDataAdapter("SELECT iD, description FROM myTable WHERE Id = @ID", con))
        {
        da.SelectCommand.Parameters.AddWithValue("@ID", myTextBox.Text);
        DataTable dt = new DataTable();
        da.Fill(dt);
        myDataGridView.DataSource = dt;
        }
    }

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