数据库方面的操作示例

1  连接SQL Server数据库示例
// 连接字符串
 string ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
// 创建SqlConnection对象
 SqlConnection connection = new SqlConnection(ConnectionString); 
  
 try
 {
  // 打开数据库连接
  connection.Open();         
  myLabel.Text = "连接数据库成功";
 }
 catch
 {
  myLabel.Text = "连接数据库失败";
 }
 finally
 {
         // 关闭数据库连接
        connection.Close();         
 }
 <appSettings>
    <add key="ConnectionSqlServer" value="Server=(local);User id=sa;Pwd=sa;Database=Northwind"></add>
 <add key="ConnectionSqlServer1" value="Server=(local);User id=sa;Pwd=sa;"></add>
 <add key="ConnectionSqlServer_tempdb" value="Server=(local);User id=sa;Pwd=sa;Database=tempdb"></add>
 <add key="ConnectionDB2" value="DATABASE=SAMPLE;UID=username;PWD=password"></add>
 <add key="ConnectionOracle" value="Data Source=Oracle8i;Integrated Security=yes"></add>
  </appSettings> 
  <system.web>

 2  // 连接到 ACCESS 的连接字符串
    string ConnStr = "Provider=Microsoft.Jet.OLEDB.4.0; Data source=" + Server.MapPath("grocertogo.mdb");
    // 使用OleDb .NET数据提供程序创建连接
    OleDbConnection oleConnection = new OleDbConnection(ConnStr);
    try
    {
     // 打开数据库连接
     oleConnection.Open();
     // 显示连接成功信息
     myLabel.Text = "Access数据库连接状态：" + oleConnection.State;
    }
    catch(Exception ex)
    {
     // 如果出现异常，显示异常信息
     myLabel.Text = "Access数据库连接状态：" + ex.ToString();
    }
    finally
    {
     // 关闭数据库连接
     oleConnection.Close(); 
    }

3 // 连接到 Oracle 数据库示例

    string ORACLE_ConnStr = "Data Source=Oracle8i;Integrated Security=yes";
    // 创建 OracleConnection 对象
    OracleConnection oConnection = new OracleConnection(ORACLE_ConnStr);
    try
    {
     oConnection.Open();
     myLabel.Text = "连接到 Oracle 数据库";
    }
    catch(Exception ex)
    {
     myLabel.Text = ex.ToString();
    }
    finally
    {
     oConnection.Close();
    }  

4 SqlCommand 执行SQL命令示例
    string ConnStr = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    // 创建SqlConnection对象
    // 创建Command对象
    SqlConnection thisConnection = new SqlConnection(ConnStr);
    SqlCommand thisCommand = new SqlCommand();
    // 关联Connection对象
    // 赋值SQL语句到CommandText属性
    // 指定命令类型是Sql语句
    thisCommand.Connection = thisConnection;
    thisCommand.CommandText = "SELECT COUNT(*) FROM Employees";
    thisCommand.CommandType = CommandType.Text;
    try
    {
     // 打开数据库连接
     thisCommand.Connection.Open();
     // 获取查询结果
     myLabel.Text = thisCommand.ExecuteScalar().ToString();
    }
    catch(SqlException ex)
    {
     // 如果出现异常，在Label标签中显示异常信息
     myLabel.Text = ex.ToString();
    }
    finally
    {
     // 关闭数据库连接
     thisCommand.Connection.Close();
    }

5  SqlDataReader 读取数据示例
   string ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    string Sql = "SELECT LastName, FirstName FROM Employees";
    SqlConnection thisConnection = new SqlConnection(ConnectionString);
    SqlCommand thisCommand = new SqlCommand(Sql, thisConnection);
    thisCommand.CommandType = CommandType.Text;
    try
    {
     // 打开数据库连接
     thisCommand.Connection.Open();
     // 执行SQL语句，并返回DataReader对象
     SqlDataReader dr = thisCommand.ExecuteReader();
     // 以粗体显示标题
     myLabel.Text = "<b>LastName FirstName</b><br>";
     // 循环读取结果集
     while(dr.Read())
     {
      // 读取两个列值并输出到Label中
      myLabel.Text += dr["LastName"] + " " + dr["FirstName"] + "<br>";
     }
     // 关闭DataReader
     dr.Close();
    }
    catch(SqlException ex)
    {
     // 异常处理
     Response.Write(ex.ToString());
    }
    finally
    {
     // 关闭数据库连接
     thisCommand.Connection.Close();
    }

6  使用DataAdapter填充数据到DataSet
        string ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    string Sql = "SELECT EmployeeID, LastName, FirstName,Title, TitleOfCourtesy, BirthDate FROM Employees";
    // 创建SqlConnection对象
    // 创建DataAdapter对象并初始化
    SqlConnection thisConnection = new SqlConnection(ConnectionString);
    SqlDataAdapter adapter = new SqlDataAdapter(Sql, thisConnection);
    // 创建DataSet对象
    DataSet data = new DataSet();
    // 填充数据到DataSet
    adapter.Fill(data);
    // 数据绑定
    myDataGrid.DataSource = data;
    myDataGrid.DataBind();

7 使用DataTable存储数据库表内容
    string ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    string Sql = "SELECT EmployeeID, LastName, FirstName, BirthDate FROM Employees";
 // 创建SqlConnection、SqlDataAdapter对象
    SqlConnection thisConnection = new SqlConnection(ConnectionString);
    SqlDataAdapter adapter = new SqlDataAdapter(Sql, thisConnection);
// 创建DataTable对象
    DataTable table = new DataTable();
 // 填充数据到DataTable
    adapter.Fill(table);
    // 将DataTable绑定到DataGrid控件
    myDataGrid.DataSource = table;
    myDataGrid.DataBind();

8 将数据库数据填充到 XML 文件
// 连接字符串及 SQL 语句
    string ConnString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    string Sql = "SELECT CustomerID,CompanyName,Country FROM Customers";
    // 连接 SqlConnection 及 SqlDataAdapter 对象
    SqlConnection thisConnection = new SqlConnection(ConnString);
    SqlDataAdapter adapter = new SqlDataAdapter(Sql, thisConnection);
    // 创建 DataSet 对象
    DataSet data = new DataSet();
    // 填充 DataSet
    adapter.Fill(data, "Customers");
    // 将 DataSet 数据其及架构填充到 Xml 文件
    data.WriteXml(Server.MapPath(".") + "\\myXml.xml", XmlWriteMode.WriteSchema);
    
    // 提示填充是否成功
    Label1.Text = "填充到XML文件成功";

9 ASP.NET 使用存储过程
   // 连接字符串
   string ConnStr = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
   // 创建Connection对象
   SqlConnection myConn = new SqlConnection(ConnStr);
   // 创建Command对象并和Connection对象关联
   SqlCommand myCommand = new SqlCommand();
   myCommand.Connection = myConn;
   
   // 指定要执行的存储过程名称
   myCommand.CommandText = "CustomersProc";
   // 使用要执行的是存储过程
   myCommand.CommandType = CommandType.StoredProcedure;
   // 创建DataAdapter对象填充数据
   DataSet myDS = new DataSet();
   SqlDataAdapter adapter = new SqlDataAdapter(myCommand);
   adapter.Fill(myDS, "Customers");
   // 将返回的数据和DataGrid绑定显示
   myDataGrid.DataSource = myDS.Tables["Customers"];
   myDataGrid.DataBind();

10 使用带输入参数的存储过程
string ConnStr = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    // 创建数据库操作对象
    SqlDataAdapter myAdapter = new SqlDataAdapter();
    SqlCommand myCommand = new SqlCommand();
    myCommand.Connection = new SqlConnection(ConnStr);
    DataTable dt = new DataTable();
    // 指定要调用的存储过程名称 "Customer_Select"
    // 指定SqlCommand对象的命令类型为 "StoredProcedure"枚举值
    myCommand.CommandText = "Customer_Select";
    myCommand.CommandType = CommandType.StoredProcedure;
    // 创建SqlParameter对象，指定参数名称、数据类型、长度及参数值
    SqlParameter para = new SqlParameter("@country", SqlDbType.NVarChar, 15);
    para.Value = DropDownList1.SelectedValue;
    
    myCommand.Parameters.Add(para);
    // 关联SqlDataAdapter与SqlCommand对象
    myAdapter.SelectCommand = myCommand;
    myAdapter.Fill(dt);
    // 绑定DataGrid
    DataGrid1.DataSource = dt;
    DataGrid1.DataBind();

11 使用带输入、输出参数的存储过程示
string ConnStr = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    // 创建 Connection 和 Command 对象
    SqlConnection myConn = new SqlConnection(ConnStr);
    SqlCommand myCommand = new SqlCommand("EmployeesProc", myConn);
    // 指定要执行的命令为存储过程
    myCommand.CommandType = CommandType.StoredProcedure;
    // 增加输入参数并赋值
    myCommand.Parameters.Add("@TitleOfCourtesy", SqlDbType.NVarChar, 20);
    myCommand.Parameters["@TitleOfCourtesy"].Value = myDropDownList.SelectedItem.Text;
    myCommand.Parameters["@TitleOfCourtesy"].Direction = ParameterDirection.Input;
    // 增加输出参数
    myCommand.Parameters.Add("@empCount", SqlDbType.Int);
    myCommand.Parameters["@empCount"].Direction = ParameterDirection.Output;
    // 创建 DataAdapter 对象填充数据
    DataSet myDS = new DataSet();
    SqlDataAdapter adapter = new SqlDataAdapter(myCommand);
    adapter.Fill(myDS, "Customers");
    // 使用 Label 控件显示输出参数的输出值
    rtnLabel.Text = myCommand.Parameters["@empCount"].Value.ToString();
    // 将返回的数据和 DataGrid 绑定显示
    myDataGrid.DataSource = myDS.Tables["Customers"];
    myDataGrid.DataBind();

12 获得数据库中表的数目和名称 获取服务器端数据库列表
string listQuery = "SELECT name FROM sysobjects WHERE xtype = 'U'";
string sumQuery = "SELECT COUNT(*) FROM sysobjects WHERE xtype = 'U'

string db_query = "sp_helpdb";

13 保存图片到SQL Server数据库示例
 // HttpPostedFile对象，用于读取图象文件属性
     HttpPostedFile UpFile = UP_FILE.PostedFile;
     // FileLength 变量存储图片的字节大小
     int FileLength = UpFile.ContentLength;
     try
     {
    if (FileLength == 0)
    {
     txtMessage.Text = "<b>您未选择上传的文件</b>";
    }
    else
    {
     // 创建存储图片文件的临时 Byte 数组
     Byte[] FileByteArray = new Byte[FileLength];
     // 建立数据流对象
     Stream StreamObject = UpFile.InputStream;  
    
     // 读取图象文件数据，FileByteArray为数据储存体，0为数据指针位置、FileLnegth为数据长度
     StreamObject.Read(FileByteArray,0,FileLength);  
     // 数据库操作
     string ConnStr = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
     string query = "INSERT INTO ImageTable (ImageData, ImageContentType, ImageDescription, ImageSize) VALUES (@ImageData, @ImageContentType, @ImageDescription, @ImageSize)";
     SqlCommand myCommand = new SqlCommand(query, new SqlConnection(ConnStr));
     // 添加各项参数并赋值
     myCommand.Parameters.Add("@ImageData", SqlDbType.Image);
     myCommand.Parameters.Add("@ImageContentType", SqlDbType.VarChar, 50);
     myCommand.Parameters.Add("@ImageDescription", SqlDbType.VarChar, 200);
     myCommand.Parameters.Add("@ImageSize", SqlDbType.BigInt);
     myCommand.Parameters["@ImageData"].Value = FileByteArray;
     myCommand.Parameters["@ImageContentType"].Value = UpFile.ContentType;
     myCommand.Parameters["@ImageDescription"].Value = txtDescription.Text;
     myCommand.Parameters["@ImageSize"].Value = FileLength;
     
     // 执行数据库操作
     myCommand.Connection.Open();
     myCommand.ExecuteNonQuery();
     myCommand.Connection.Close();
     // 提示上传成功
     txtMessage.Text = "<b>上传文件成功</b>";
    }
   } 
   catch (Exception ex) 
   {
    // 使用 Label 标签显示异常
    txtMessage.Text = ex.Message.ToString();
   }

14 获得插入记录标识号的示例
// 数据库连接字符串
    string ConnStr = System.Configuration.ConfigurationSettings.AppSettings["ConnectionSqlServer"];
    // 创建插入SQL语句及调用@@identity函数返回标识值
    string insert_query = "insert into Categories (CategoryName,Description) values ('IT', 'Internet');"
      + "SELECT @@identity AS 'identity';";
    // 执行数据库操作
    SqlCommand myCommand = new SqlCommand(insert_query, new SqlConnection(ConnStr));
    myCommand.Connection.Open();
    myLabel.Text = myCommand.ExecuteScalar().ToString();
    myCommand.Connection.Close();
15 如何读取Excel表格中的数据
      // 获取Excep文件的完整路径
    string source = File1.Value;
    string ConnStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + source + ";Extended Properties=Excel 8.0";
    string query = "SELECT * FROM [Sheet1$]";
    OleDbCommand oleCommand = new OleDbCommand(query, new OleDbConnection(ConnStr));
    OleDbDataAdapter oleAdapter = new OleDbDataAdapter(oleCommand);
    DataSet myDataSet = new DataSet();
    // 将 Excel 的[Sheet1]表内容填充到 DataSet 对象
    oleAdapter.Fill(myDataSet, "[Sheet1$]");
    // 数据绑定
    DataGrid1.DataSource = myDataSet;
    DataGrid1.DataMember = "[Sheet1$]";
    DataGrid1.DataBind();