使用ADO.NET查询和操作数据
使用ADO.NET查询和操作数据
StringBuilder类： 用来定义可变字符串
StringBuilder sb = new StringBuilder("");
//追加字符串
sb.Append("World");
sb.Append("!");
//W2orld
sb.Insert(2, "2");
//原字符串：Wo2rld! 截取之后：W2rld!
sb.Remove(1, 2);
//ToString()
Console.WriteLine(sb.ToString());
查询学生记录数
//打开数据库连接
con.Open();
//使用StringBuilder追加SQL语句
StringBuilder sb = new StringBuilder();
sb.Append("select ");
sb.Append(" Count(*) ");
sb.Append(" from ");
sb.Append("[Student]");
Console.WriteLine(sb.ToString());
//创建一个SqlCommand对象
SqlCommand com = new SqlCommand(sb.ToString(),con);
Console.WriteLine((int)com.ExecuteScalar());
DataReader：从数据源中检索只读、只进的数据流，每次读取一行数据
StringBuilder sb = new StringBuilder();
sb.AppendLine("select");
sb.AppendLine("[StudentNo]");
sb.AppendLine(",[StudentName]");
sb.AppendLine("from");
sb.AppendLine("[Student]");
SqlCommand com = new SqlCommand(sb.ToString(), con);
//从数据源中检索只读、只进的数据流
return com.ExecuteReader();
SqlDataReader reader=GetStudentInfo();
while (reader.Read())
{
Console.WriteLine("{0}\t{1}",reader["StudentNo"],reader["StudentName"]);
}
reader.Close();
ExecuteNonQuery():
StringBuilder sb = new StringBuilder();
sb.AppendLine("Insert into");
sb.AppendLine("[Grade]([GradeName])");
sb.AppendLine("Values('" + gradeName + "')");
//3.创建一个SqlCommand
SqlCommand com = new SqlCommand(sb.ToString(),con);
//4.返回执行结果
return com.ExecuteNonQuery();
Student stu = new Student();
Console.WriteLine("请输入年级名称：");
string gradename = Console.ReadLine();
int count = stu.AddGrade(gradename);
if (count > 0)
{
Console.WriteLine("success！");
}
else
{
Console.WriteLine("success mother!");
}
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class Test { string connString = "Data Source = .;Initial Catalog= Library;User Id = Sa;Pwd = asiga0."; //判断用户 public bool CheckUser(string UserId, string Password) { String s = "select count(*) from user1 where loginid='" + UserId + "'and loginpwd = '" + Password + "'";//空格错误! SqlConnection conn = new SqlConnection(connString); SqlCommand comm = new SqlCommand(s, conn); try { conn.Open(); if ((int)comm.ExecuteScalar()>0 ) { Console.WriteLine("登陆成功"); return true; } else { Console.WriteLine("登录失败"); return false; } } catch (Exception ex) { Console.WriteLine(ex.Message); return false; } finally { conn.Close(); } } //主菜单 public void List() { do { Console.WriteLine("====请选择操作键===="); Console.WriteLine("1.查看全部图书"); Console.WriteLine("2.插入图书信息"); Console.WriteLine("3.修改图书信息"); Console.WriteLine("4.删除图书信息"); Console.WriteLine("5.退出"); Console.WriteLine("==============="); int i = int.Parse(Console.ReadLine()); switch (i) { case 1: One(); break; case 2: Two(); break; case 3: Three(); break; case 4: Four(); break; case 5: Console.WriteLine("谢谢使用,再见!"); return; default: break; } Console.WriteLine("继续吗?(Y/N)"); if (!Console.ReadLine().ToLower().Trim().Equals("y")) { break; } } while (true); } public void One() { SqlConnection conn = new SqlConnection(connString); try { String s = "select book.id,book.name,booktype.typename,book.number,book.price from book,booktype where book.typle=booktype.typle"; Console.WriteLine("------------------------------------------------"); Console.WriteLine("编号\t名称\t\t类别\t数量\t价格"); Console.WriteLine("------------------------------------------------"); SqlCommand comm = new SqlCommand(s, conn); conn.Open(); SqlDataReader rd = comm.ExecuteReader(); while (rd.Read()) { Console.WriteLine("{0}\t{1}\t{2}\t{3}\t{4}", rd["id"], rd["name"], rd["typename"], rd["number"], rd["price"]);//前面不能加" . " } rd.Close(); } catch (Exception ex) { Console.WriteLine(ex.Message); } finally { conn.Close(); } } public void Two() { SqlConnection conn = new SqlConnection(connString); try { Console.WriteLine("请输入图书编号"); int Id = int.Parse(Console.ReadLine()); if (GetBookByID(Id)) { Console.WriteLine("图书记录已存在,请重新输入!"); return; } Console.WriteLine("请输入图书名称"); string name = Console.ReadLine(); Console.WriteLine("请插入图书类型编号"); int type = int.Parse(Console.ReadLine()); if (GetBookTypeByID(type)) { } else { Console.WriteLine("不存在,请重新输入"); return; } Console.WriteLine("请插入图书数量"); int number = int.Parse(Console.ReadLine()); Console.WriteLine("请输入图书单价"); float price = float.Parse(Console.ReadLine()); String s = string.Format("insert book(id,name,typle,number,price) values({0},'{1}',{2},{3},{4})", Id, name, type, number, price); SqlCommand comm = new SqlCommand(s, conn); conn.Open();//忘记开启 if (comm.ExecuteNonQuery() > 0) { Console.WriteLine("插入成功!"); } else { Console.WriteLine("插入失败"); } } catch (Exception ex) { Console.WriteLine(ex.Message); } finally { conn.Close(); } } public bool GetBookByID(int bookId) { SqlConnection conn = new SqlConnection(connString); string s = "select id from book where id=" + bookId; SqlCommand comm = new SqlCommand(s, conn); conn.Open(); SqlDataReader rd = comm.ExecuteReader(); try { if (rd.Read()) { return true; } else { return false; } } catch (Exception ex) { Console.WriteLine(ex.Message); return true; } finally { rd.Close(); conn.Close(); } } public bool GetBookTypeByID(int typeId) { SqlConnection conn = new SqlConnection(connString); string s = "select typle,typename from booktype where typle=" + typeId; SqlCommand comm = new SqlCommand(s, conn); conn.Open(); SqlDataReader rd = comm.ExecuteReader(); try { if (rd.Read()) { Console.WriteLine("{0}\t{1}", rd["typle"], rd["typename"]); return true; } else { return false; } } catch (Exception ex) { Console.WriteLine(ex.Message); return false; } finally { rd.Close(); conn.Close(); } } public void Three() { Console.WriteLine("请输入图书编号"); int id = int.Parse(Console.ReadLine()); if (GetBookByID(id)) { Console.WriteLine("请输入修改后的价格($.00):"); float f = float.Parse(Console.ReadLine()); if (ChangePrice(id, f) > 0) { Console.WriteLine("修改成功"); } else { Console.WriteLine("修改失败"); } } else { Console.WriteLine("不存在该编号,请重新输入"); return; } } public int ChangePrice(int id,float price) { SqlConnection conn = new SqlConnection(connString); try { String s = string.Format("update book set price ={0} where id={1}", price, id); SqlCommand comm = new SqlCommand(s, conn); conn.Open(); return comm.ExecuteNonQuery(); } catch (Exception ex) { Console.WriteLine(ex.Message); return -1; } finally { conn.Close(); } } public void Four() { Console.WriteLine("请输入图书编号"); int id = int.Parse(Console.ReadLine()); if (GetBookByID(id)) { show(id); Console.WriteLine("将删除该图书记录,确认吗?(Y/N)"); if (Console.ReadLine().ToLower().Trim().Equals("y")) { if (DeleteBookByID(id) > 0) { Console.WriteLine("修改成功"); } else { Console.WriteLine("修改失败"); } } else { Console.WriteLine("未删除,返回"); } } else { Console.WriteLine("编号不存在,重新输入"); return; } } public void show(int id) { SqlConnection conn = new SqlConnection(connString); try { String s = "select book.id,book.name,booktype.typename,book.number,book.price from book,booktype where book.typle=booktype.typle and book.id="+id; Console.WriteLine("------------------------------------------------"); Console.WriteLine("编号\t名称\t\t类别\t数量\t价格"); Console.WriteLine("------------------------------------------------"); SqlCommand comm = new SqlCommand(s, conn); conn.Open(); SqlDataReader rd = comm.ExecuteReader(); while (rd.Read()) { Console.WriteLine("{0}\t{1}\t{2}\t{3}\t{4}", rd["id"], rd["name"], rd["typename"], rd["number"], rd["price"]);//前面不能加" . " } rd.Close(); } catch (Exception ex) { Console.WriteLine(ex.Message); } finally { conn.Close(); } } public int DeleteBookByID(int id) { SqlConnection conn = new SqlConnection(connString); String s = "Delete from book where id=" + id; SqlCommand comm = new SqlCommand(s, conn); try { conn.Open(); return comm.ExecuteNonQuery(); } catch (Exception ex) { Console.WriteLine(ex.Message); return -1; } finally { conn.Close(); } } |
