为啥会报上下文不存在sql Connection1啊？

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.IO;

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

    private void btQuery_Click(object sender, EventArgs e)
    {
        sqlConnection.Open();
        ds = new DataSet();
        string sql;
        if (dormid.Text.Trim() == "")
            sql = "select * from register where datecome='" + date.Value.Date.ToString() + "'";
        else
            sql = "select * from register where dormid like '%" + dormid.Text.Trim() + "%'";
        SqlDataAdapter adp = new SqlDataAdapter(sql, sqlConnection);
        adp.Fill(ds, "register");
        DataTable dt = ds.Tables[0];
        dt.Columns["registerid"].ColumnName = "编号";
        dt.Columns["dormid"].ColumnName = "宿舍号";
        dt.Columns["comename"].ColumnName = "来访人";
        dt.Columns["datecome"].ColumnName = "来访时间";
        dt.Columns["lookname"].ColumnName = "被访人";
        dt.Columns["dateleave"].ColumnName = "离开时间";
        dt.Columns["remark"].ColumnName = "备注";
        dataGridView1.DataSource = dt;
        for (int i = 0; i < this.dataGridView1.Rows.Count; )
        {
            this.dataGridView1.Rows[i].DefaultCellStyle.BackColor = System.Drawing.Color.LightBlue;

            i += 2;
        }
        sqlConnection.Close();
    }

    private void btDelete_Click(object sender, EventArgs e)
    {
          if (this.dataGridView1.CurrentRow != null)
        {
            sqlConnection1.Open();
            string sql = "delete from register where registerid='" + ds.Tables[0].Rows[dataGridView1.CurrentRow.Index][0].ToString().Trim() + "'";
            if (MessageBox.Show("你真的要删除该条信息吗？", "提示", MessageBoxButtons.YesNo) == DialogResult.Yes)
            {
                SqlCommand cmd = new SqlCommand(sql, sqlConnection1);
                cmd.ExecuteNonQuery();
                MessageBox.Show("删除'" + ds.Tables[0].Rows[dataGridView1.CurrentRow.Index][4].ToString().Trim() + "'成功！", "提示");
                sqlConnection1.Close();
            }
            else
                sqlConnection1.Close();
        }
    }
}

}

sqlConnection.Open();
这里报错么
如果这里不报错

下面所有的sqlConnection1全部修改为sqlConnection