三、DataSet数据集的操作

1.DataSet的显示

string connStr = "server=.;uid=sa;pwd=123;database=testDb";
using (SqlConnection conn = new SqlConnection(connStr))
{
     //实例化一个数据集
     DataSet ds = new DataSet();
     //数据适配器，用于DataSet和SQL数据库的连接
     SqlDataAdapter sda = new SqlDataAdapter("select * from employee ", conn);
     //在DataSet中添加或刷新行
     sda.Fill(ds);
     //将ds中的表显示到dataGridView1控件中
     dataGridView1.DataSource = ds.Tables[0];
}

2.DataSet的合并

string connStr = "server=.;uid=sa;pwd=123,;database=testDb";
using (SqlConnection conn = new SqlConnection(connStr))
{
     //实例化数据集ds1
     DataSet ds1 = new DataSet();
     SqlDataAdapter sda1 = new SqlDataAdapter("select * from employee", conn);
     sda1.Fill(ds1);
     //实例化数据集ds2
     DataSet ds2 = new DataSet();
     SqlDataAdapter sda2 = new SqlDataAdapter("select * from testTable2", conn);
     //在DataSet中添加或刷新行
     sda2.Fill(ds2);
     //将ds2与ds1合并，并处理不兼容的架构
     ds1.Merge(ds2, true,MissingSchemaAction.AddWithKey);
     this.dataGridView1.DataSource = ds1.Tables[0];
}

3.DataSet的复制

//数据集ds1
DataSet ds1;
private void Form1_Load(object sender, EventArgs e)
{
      string connStr = "server=.;uid=sa;pwd=123;database=TestDb";
      using (SqlConnection conn = new SqlConnection(connStr))
      {
           //SqlDataAdapter 数据一次性加载完成，连接就关闭了（数据量大的时候）
           //SqlDataReader 数据一行一行读取，需要手动关闭连接（数据量小的时候）
           using (SqlDataAdapter sda = new SqlDataAdapter("select * from employee", conn))
           {
                ds1 = new DataSet();
                sda.Fill(ds1);
                dataGridView1.DataSource = ds1.Tables[0];
           }
      }
}

private void button1_Click(object sender, EventArgs e)
{
     //复制ds1的数据和结构到ds2
     DataSet ds2 = ds1.Copy();
     dataGridView2.DataSource = ds2.Tables[0];
}

4.DataSet的更新

DataSet ds1;
SqlDataAdapter sda;
private void button1_Click(object sender, EventArgs e)
{
      string connStr = "server=.;uid=sa;pwd=123;database=TestDb";
      //SqlConnection conn = new SqlConnection(connStr);
      SqlConnection conn = new SqlConnection(connStr);
      SqlCommand cmd = conn.CreateCommand();
      cmd.CommandText = "select * from employee";
      sda = new SqlDataAdapter();
      sda.SelectCommand = cmd;
      ds1 = new DataSet();
      sda.Fill(ds1, "oldDs");
      dataGridView1.DataSource = ds1.Tables[0];
}

private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
{
      textBox1.Text = dataGridView1.SelectedCells[0].Value.ToString();
      textBox2.Text = dataGridView1.SelectedCells[1].Value.ToString();
      textBox3.Text = dataGridView1.SelectedCells[2].Value.ToString();
      textBox4.Text = dataGridView1.SelectedCells[3].Value.ToString();
      textBox5.Text = dataGridView1.SelectedCells[4].Value.ToString();
}

private void button2_Click(object sender, EventArgs e)
{
      DataTable dt = ds1.Tables["oldDs"];
      //将表结构加载到表中
      sda.FillSchema(dt, SchemaType.Mapped);
      DataRow dr = dt.Rows.Find(textBox1.Text);
      dr["name"] = textBox2.Text;
      dr["gender"] = textBox4.Text;
      dr["money"] = textBox3.Text;
      dr["salary"] = textBox5.Text;
      //用于对数据集DataSet进行更改操作，同时作用于关联的数据库
      SqlCommandBuilder scbd = new SqlCommandBuilder(sda);
      //更新DataTable中的数据
      sda.Update(dt);
      //sda.Update(ds1, "oldDs");
}