將 varchar 數值 'GridView1.DataKeys[gvr.DataItemIndex].Value' 轉換成資料型別為 int 的資料行語法錯誤。

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            string connStr = ConfigurationManager.ConnectionStrings["BTS"].ConnectionString;
            SqlConnection conn = new SqlConnection(connStr);
            conn.Open();
            DataSet ds = new DataSet();
            SqlCommand comm = new SqlCommand();
            SqlDataAdapter sqlad = new SqlDataAdapter();
            comm.Connection = conn;
            comm.CommandText = "select * from bts";
            sqlad.SelectCommand = comm;
            //Response.Write(sqlad.SelectCommand.CommandText);
            sqlad.Fill(ds, "bts");
            GridView1.DataSource = ds.Tables["bts"];
            GridView1.DataBind();
        }
    }
protected void Button3_Click(object sender, EventArgs e)
    {
        foreach (GridViewRow gvr in GridView1.Rows)
        {
            CheckBox ch = (CheckBox)gvr.FindControl("ItemCheckBox");
            if (ch.Checked)
            {
                //Ret2.Text += "<li>GridView1 您选择的是（键值）：" + GridView1.DataKeys[gvr.DataItemIndex].Value.ToString();
                string connStr = ConfigurationManager.ConnectionStrings["BTS"].ConnectionString;
                SqlConnection conn = new SqlConnection(connStr);
                conn.Open();
                DataSet ds = new DataSet();
                SqlCommand comm = new SqlCommand();
                SqlDataAdapter sqlad = new SqlDataAdapter();
                string sql;
                sql = "delete from bts where au_id= 'GridView1.DataKeys[gvr.DataItemIndex].Value'";
                comm.Connection = conn;
                comm.CommandText = sql;
                comm.ExecuteNonQuery();

            }
        }
    }

    protected void CheckAll(object sender, EventArgs e)
    {
        CheckBox cbx = (CheckBox)sender;
        foreach (GridViewRow gvr in GridView1.Rows)
        {
            CheckBox ch = (CheckBox)gvr.FindControl("ItemCheckBox");
            ch.Checked = cbx.Checked;
        }
    }