winform 监视DataGridView的滚动条，加载数据

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.IO;
using System.Data.SqlClient;

namespace temp
{
public partial class ttt : Form
{
public ttt()
{
InitializeComponent();
}

SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=ManageDatas;integrated security=true;");

int index = 1;
/// <summary>
/// 是否继续加载数据
/// </summary>
bool getDataContinue = true;

private void ttt_Load(object sender, EventArgs e)
{
//this.WindowState = FormWindowState.Maximized;
do
{
AddNew();
} while (Verify());
}

private void button1_Click(object sender, EventArgs e)
{

}

/// <summary>
/// 加载数据
/// </summary>
void AddNew()
{
DataTable newData = GetData(index);
if (newData != null && newData.Rows.Count > 0)
{
if (dataGridView1.Columns.Count == 0)
for (int i = 0; i < newData.Columns.Count; i++)
dataGridView1.Columns.Add(newData.Columns[i].ColumnName, newData.Columns[i].ColumnName);
foreach (DataRow dr in newData.Rows)
{
int newIndex = dataGridView1.Rows.Add();
for (int i = 0; i < dr.ItemArray.Count(); i++)
dataGridView1.Rows[newIndex].Cells[i].Value = dr[i];
}
}
else
getDataContinue = false;
}

/// <summary>
/// 获取指定页数据
/// </summary>
DataTable GetData(int page,int size=20)
{
string sqlstr = string.Format(@"WITH TB AS (SELECT ROW_NUMBER()OVER(ORDER BY intid ASC) AS rowid,* FROM tblbuyermsg)
SELECT * FROM TB  WHERE rowid between {0} and {1}", (page - 1) * size + 1, page * size);
SqlDataAdapter da = new SqlDataAdapter(sqlstr, conn);
DataTable dt = new DataTable();
da.Fill(dt);
index++;
return dt;
}

/// <summary>
/// 验证是否需要加载数据
/// </summary>
/// <returns>需要加载则返回true</returns>
bool Verify()//gridView高度不能太低
{
if (!getDataContinue)
return false;
bool bottom = false;
//若gridView高度太低，则考虑
if (dataGridView1.Height < 40 && dataGridView1.FirstDisplayedScrollingRowIndex > dataGridView1.Rows.Count - 3)
bottom = true;
else
{
int rowsHeight = 0;
for (int i = dataGridView1.FirstDisplayedScrollingRowIndex; i < dataGridView1.Rows.Count; i++)
{
//if (i < 0) i = 0;
rowsHeight += dataGridView1.Rows[i].Height;
if (rowsHeight - dataGridView1.Height > 30)
{
return false;
}
}
bottom = true;
}
return bottom;
}

private void dataGridView1_Scroll(object sender, ScrollEventArgs e)
{
if (Verify())
AddNew();
}

private void dataGridView1_Resize(object sender, EventArgs e)
{
do
{
AddNew();
} while (Verify());
}
}
}