無(wú)連接模式：可以在沒(méi)有打開(kāi)連接時(shí)在內(nèi)存中操作數(shù)據(jù)，DataAdapter通過(guò)管理連接為無(wú)連接模式提供服務(wù)，當(dāng)要從數(shù)據(jù)庫(kù)中查詢數(shù)據(jù)時(shí)，DataAdapter打開(kāi)一個(gè)連接，填充指定的DataSet,等數(shù)據(jù)讀取完馬上自動(dòng)關(guān)閉連接，然后可以對(duì)數(shù)據(jù)做修改，再次使用DataAdapter打開(kāi)連接，持久化修改(無(wú)論是更新，刪除或是更新)，最后自動(dòng)關(guān)閉連接，使用無(wú)連接模式的情況是有一些獨(dú)立數(shù)據(jù)，它們不會(huì)發(fā)生改變或者很少改變，因?yàn)樵趯⑻畛銬ataSet和更新數(shù)據(jù)這段時(shí)間內(nèi)數(shù)據(jù)庫(kù)中的實(shí)際數(shù)據(jù)也許會(huì)發(fā)生改變，如果需要將數(shù)據(jù)立即持久化到數(shù)據(jù)庫(kù)請(qǐng)使用連接模式
讀取數(shù)據(jù)到DataSet:無(wú)連接意味著一個(gè)連接建立了一個(gè)與數(shù)據(jù)庫(kù)的會(huì)話，請(qǐng)求的數(shù)據(jù)讀入到DataSet中，然后通過(guò)斷開(kāi)數(shù)據(jù)庫(kù)的連接關(guān)閉會(huì)話，這時(shí)會(huì)話因?yàn)榕c數(shù)據(jù)庫(kù)的斷開(kāi)而關(guān)閉，DataSet成為一個(gè)無(wú)連接的數(shù)據(jù)庫(kù)
復(fù)制代碼 代碼如下:
/// summary>
/// 查詢學(xué)生信息
/// /summary>
/// returns>返回填充了學(xué)生表的DataSet/returns>
public DataSet GetUserInfor()
{
string str = "Data Source=.;Initial Catalog=Student;Integrated Security=True";
var conn = new SqlConnection(str);
DataSet ds = new DataSet();
var sda = new SqlDataAdapter("SELECT * FROM Student",conn);
sda.Fill(ds, "student");//調(diào)用fill方法時(shí)，SqlDataAdapter會(huì)自動(dòng)打開(kāi)連接，讀取數(shù)據(jù)然后關(guān)閉連接
foreach (DataRow dr in ds.Tables["student"].Rows)
{
Console.WriteLine(dr["name"]);
}
return ds;
}
將DataSet的修改保存到數(shù)據(jù)庫(kù)
插入數(shù)據(jù)
復(fù)制代碼 代碼如下:
/// summary>
/// 插入學(xué)生信息，并返回插入后的DataSet
/// /summary>
/// param name="stu">學(xué)生實(shí)體類/param>
public DataSet InsertStudnt(Student stu)
{
DataSet ds = GetUserInfor();
string str = "Data Source=.;Initial Catalog=Student;Integrated Security=True";
string sql = "INSERT INTO student VALUES (@name,@age)";
var conn = new SqlConnection(str);
var cmd = new SqlCommand(sql,conn);
var sda = new SqlDataAdapter();
SqlParameter sqlParam1 = new SqlParameter()
{
ParameterName = "@name",
SourceColumn = "name"
};
SqlParameter sqlParam2 = new SqlParameter()
{
ParameterName = "@age",
SourceColumn = "age"
};
SqlParameter[] sqlParamArray = new SqlParameter[] {sqlParam1,sqlParam2 };
cmd.Parameters.AddRange(sqlParamArray);
sda.InsertCommand = cmd;
DataRow dr = ds.Tables["student"].NewRow();
dr["name"] = stu.name;
dr["age"] = stu.age;
ds.Tables["student"].Rows.Add(dr);
sda.Update(ds,"student");
return ds;
}
更新數(shù)據(jù)
復(fù)制代碼 代碼如下:
/// summary>
/// 根據(jù)ID更新姓名和年齡
/// /summary>
/// param name="name">姓名/param>
/// param name="age">年齡/param>
/// param name="id">學(xué)生ID/param>
/// returns>返回更新后的DataSet/returns>
public DataSet UpdateStudent(Student stu,int id)
{
DataSet ds = GetUserInfor();
string str = "Data Source=.;Initial Catalog=Student;Integrated Security=True";
string sql = "UPDATE student SET name=@name,age=@age WHERE id=@id";
var conn = new SqlConnection(str);
var cmd = new SqlCommand(sql, conn);
var sda = new SqlDataAdapter();
SqlParameter param1 = new SqlParameter()
{
ParameterName="@name",SourceColumn="name"
};
SqlParameter param2 = new SqlParameter()
{
ParameterName = "@age",
SourceColumn = "age",
SqlDbType=SqlDbType.Int
};
SqlParameter param3 = new SqlParameter()
{
ParameterName = "@id",
SourceColumn = "id"
};
SqlParameter[] param = new SqlParameter[] {param1,param2,param3 };
cmd.Parameters.AddRange(param);
sda.UpdateCommand = cmd;
DataTable dt = ds.Tables["student"];
foreach (DataRow dr in dt.Rows)
{
int oldID=Convert.ToInt32(dr["id"]);
if (oldID == id)
{
dr["name"] = stu.name;
dr["age"] = stu.age;
}
}
sda.Update(ds,"student");
return ds;
}
刪除數(shù)據(jù)
復(fù)制代碼 代碼如下:
/// summary>
/// 根據(jù)ID刪除一個(gè)學(xué)生
/// /summary>
/// param name="id">返回更新后的DataSet/param>
public DataSet DeleteStudent(int id)
{
DataSet ds = GetUserInfor();
string str = "Data Source=.;Initial Catalog=Student;Integrated Security=True";
string sql = "DELETE FROM student WHERE id=@id";
var conn = new SqlConnection(str);
var cmd = new SqlCommand(sql, conn);
var sda = new SqlDataAdapter();
SqlParameter param = new SqlParameter()
{
ParameterName="@id",SourceColumn="id",SqlDbType=SqlDbType.Int
};
cmd.Parameters.Add(param);
sda.DeleteCommand = cmd;
DataTable dt=ds.Tables["student"];
foreach (DataRow dr in dt.Rows)
{
int oldId = Convert.ToInt32(dr["id"]);
if (oldId == id)
dr.Delete();
}
sda.Update(ds,"student");
return ds;
}
