多条件查询

private void button1_Click(object sender, EventArgs e)
        {
            StringBuilder sql =new StringBuilder("select * from tblBook");
            List<string> list=new List<string>();
            List<SqlParameter> listspt = new List<SqlParameter>();
            if(textBox1.Text.Trim().Length>0)
            {
                list.Add("title like '@title'");
                SqlParameter spt = new SqlParameter("@title","%"+ textBox1.Text.Trim()+"%");
                listspt.Add(spt);
                //sql.Append("title=@title");
            }
            if (textBox2.Text.Trim().Length > 0)
            {
                list.Add("public like '@public'");
                SqlParameter spt = new SqlParameter("@public","%"+ textBox2.Text.Trim()+"%");
                listspt.Add(spt);
                //sql.Append("public=@public");
            }
            if (textBox3.Text.Trim().Length > 0)
            {
                list.Add("author like '@author'");
                SqlParameter spt = new SqlParameter("@author","%"+ textBox3.Text.Trim()+"%");
                listspt.Add(spt);
                //sql.Append("anthor=@anthor");
            }
            if (list.Count > 0)
            {
                sql.Append(" where "+string.Join(" and ",list.ToArray()));
            }
            MessageBox.Show(sql.ToString());
        }