vs未对对象引用设置到对象的实例，怎么改啊

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public partial class    Form6 : Form
{
   
    public Form6()
    { 
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        
        string sname = this.textBox1.Text;
        SqlConnection conn = new SqlConnection(@"Data Source=LAPTOP-HIUQTNAV;Initial Catalog=demo;Integrated Security=True");
        string sql = string.Format("select sno,sname,sex,age,dept from dbo.student where sname like '%{0}%'",sname);
        SqlCommand cmd = new SqlCommand(sql,conn);
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        sda.Fill(ds, "student");
        this.dataGridView1.DataSource =ds.Tables["student"];






    }

    private void button5_Click(object sender, EventArgs e)
    {

    }

    private void Form6_Load(object sender, EventArgs e)
    {
        getdata();
    }
    public void getdata()
    {
        SqlConnection conn = new SqlConnection(@"Data Source=LAPTOP-HIUQTNAV;Initial Catalog=demo;Integrated Security=True");
        string sql = string.Format("select sno,sname,sex,age,dept from dbo.student");
        SqlCommand cmd = new SqlCommand(sql, conn);
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        sda.Fill(ds, "student");
        this.dataGridView1.DataSource = ds.Tables["student"];
           
        


    }

    private void button2_Click(object sender, EventArgs e)
    {
         Form7 fr7 = new Form7();
        fr7.Show(); 

    }

using System;
using System.Collections.Generic;
using System.Component

列为空

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