ConnectionString＝ "server=.;uid=账号;pwd=密码;database=数据库名";//. 表示本机 如果你是express版数据库，要写成./sqlexpress
SqlConnection   myConnection=new   SqlConnection(ConnectionString); 

string SqlStr = string.Format("select 书描述字段 from 表名 where 书名字段='{0}'", TextBox1.Text);

SqlCommand   mySqlCommand=new SqlCommand(SqlStr,myConnection); 
SqlDataReader   MyDataReader =   mySqlCommand.ExecuteReader(); 

string getValue ="";
if(MyDataReader.Read()) 
{ 
      if (!Object.Equals(dr["书描述字段"], DBNull.Value))
                   getValue  = Convert.ToString(dr["书描述字段"]);

}