c#数据操作：数据库访问 和 文件操作

SqlConnection myCon = new SqlConnection();
myCon.ConnectionString = "Persist Security Info=False;User id=sa;pwd=123;database=northwind;server=(local)";
myCon.Open();

//使用SqlCommand
SqlCommand selectCMD = new SqlCommand();
selectCMD.Connection=myCon;
selectCMD.CommandText="SELECT top 10 CustomerID, CompanyName FROM Customers";

//使用修改一行数据，完成非查询的SQL操作
selectCMD.CommandText="UPDATE Customers SET CompanyName='Wangminli' WHERE CustomerID = 'ALFKI'";
int i=selectCMD.ExecuteNonQuery();//非查询命令
Console.WriteLine("{0}行被修改。",i);   //输出：1行被修改。

//断开连接
myCon.Close();

//连接数据库
SqlConnection myCon = new SqlConnection("Persist Security Info=False;User id=sa;pwd=123;database=northwind;server=(local)");
myCon.Open();

//使用SqlCommand
SqlCommand selectCMD = new SqlCommand("SELECT top 10 CustomerID, CompanyName FROM Customers",myCon);

//获取数据适配器
SqlDataAdapter custDA = new SqlDataAdapter();
custDA.SelectCommand = selectCMD;

//提交查询，获取结果数据集
DataSet custDS=new DataSet();
custDA.Fill(custDS);

//断开连接
myCon.Close();

//连接数据库
SqlConnection myCon = new SqlConnection();
myCon.ConnectionString = "Persist Security Info=False;User id=sa;pwd=123;database=northwind;server=(local)";
myCon.Open();

//使用SqlCommand提交查询命令
SqlCommand selectCMD = new SqlCommand("SELECT  CustomerID, CompanyName FROM Customers", myCon);

//获取数据适配器
SqlDataAdapter custDA = new SqlDataAdapter();
custDA.SelectCommand = selectCMD;

//填充DataSet
DataSet custDS = new DataSet();
custDA.Fill(custDS, "Customers");
//显示XML格式的数据
//Console.WriteLine("{0}",custDS.GetXml());

//显示其中的DataTable对象中的数据
for(int i=0;i<custDS.Tables[0].Rows.Count;i++)
{
for(int j=0;j<custDS.Tables[0].Columns.Count;j++)
{
Console.Write("{0}    ",custDS.Tables[0].Rows[i].ItemArray[j]);
}
Console.WriteLine();
}

//断开连接
myCon.Close();
Console.Read();

//连接数据库
SqlConnection myCon = new SqlConnection("Persist Security Info=False;User id=sa;pwd=123;database=northwind;server=(local)");
myCon.Open();

//使用SqlCommand
SqlCommand selectCMD = new SqlCommand("SELECT top 10 CustomerID, CompanyName FROM Customers",myCon);

//创建SqlDataReader
SqlDataReader custDR=selectCMD.ExecuteReader();

//输出查询的数据
while(custDR.Read())
{
Console.Write("{0}    ",custDR.GetString(custDR.GetOrdinal("CustomerID")));
Console.Write("{0}    ",custDR.GetString(custDR.GetOrdinal("CompanyName")));
Console.WriteLine();
}
//断开连接
myCon.Close();

class Class1
{
StreamWriter
///<summary>
///在当前目录下，创建文件test.txt
///</summary>
private void CreateFile()
{
string fileName=".\\test.txt";  //当前目录为工程文件下的\bin\Debug
File.Create(fileName);          //使用File的Create静态方法
}

///<summary>
///文件拷贝方法
///</summary>
private void CopyFile()
{
string sourceFileName=".\\test.txt";   //源文件
string destFileName="D:\\test.txt";       //目标文件
File.Copy(sourceFileName,destFileName,true);  //使用File的Copy静态方法
}

///<summary>
///文件改名
///</summary>
private void RenameFile()
{
string oldFileName=".\\test.txt";      //旧文件
string newFileName=".\\test2.txt";     //新文件
File.Move(oldFileName,newFileName);    //使用File的Copy静态方法
}

///<summary>
///删除文件
///</summary>
private void DeleteFile()
{
string fileName=".\\test2.txt";    //旧文件
File.Delete(fileName);             //使用File的Delete静态方法
}

///<summary>
///文件写入
///</summary>
private void WriteFile()
{
string fileName=".\\test.txt";            //文件名
StreamWriter writer=new StreamWriter(fileName,false,System.Text.Encoding.Default);  //构造一个StreamWriter
writer.WriteLine("Hello StreamWriter!");  //向文件写入一行数据
writer.Flush();                           //写入缓冲区的数据
writer.Close();
}

///<summary>
///文件读取
///</summary>
private void ReadFile()
{
string fileName=".\\test.txt";  //文件名
StreamReader reader=new StreamReader(fileName,System.Text.Encoding.Default,false,1024);
string line=reader.ReadLine();  //读取
Console.WriteLine(line);    //输出
reader.Close();
Console.Read();
}

///<summary>
///应用程序的主入口点。
///</summary>
[STAThread]
static void Main(string[] args)
{
Class1c=new Class1();
//c.CreateFile();
//c.CopyFile();
//c.RenameFile();
//c.WriteFile();
c.ReadFile();
}