在ADO.net SQL中使用事務

Question

我是ADO的新手，所以我想問一下我是否正確使用了事務。 這里的代碼片段

string SQL1 = "INSERT INTO tbl_cust(cust_id,cust_name) values ('000001','YoungMcD') ";
string SQL2 = "UPDATE tbl_cust SET custname='OldMcDonald' WHERE cust_id='000001'";
string SQL3 = "SELECT * FROM tbl_supplier WHERE supplier_code ='000001'";

// write connstring
string conn = System.Configuration.ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
// end of connection string

// setting connection
SqlConnection db = new SqlConnection(conn);
SqlTransaction transaction1;

db.Open();
transaction1 = db.BeginTransaction();

try
{
    // insert to table
    SqlCommand Com1 = new SqlCommand(SQL1, db, transaction1);
    Com1.ExecuteNonQuery();

    SqlCommand Com2 = new SqlCommand(SQL2, db, transaction1);
    Com2.ExecuteNonQuery();

    SqlCommand Com3 = new SqlCommand(SQL3, db, transaction1);
    Com3.ExecuteNonQuery();

    transaction1.Commit();

    db.Close();
}
catch
{
    transaction1.Rollback();
    db.Close();
    msg = "error";
    goto endret;
}

對於交易，我應該使用

SqlCommand Com1 = new SqlCommand(SQL1, db, transaction1);

代替

SqlCommand Com1 = new SqlCommand(SQL1, db);

因為我已經在try{}語句之前聲明開始交易

編輯：

我明白了，First語法適用，但是如何有效使用ADO？ 我發現這種方式太簡單了。

我發現自己繼續這樣做是為了插入參數，例如：

string SQL1 = "INSERT INTO tbl_cust(cust_id,cust_name) values ('" + param1 +"','"+ param2 +"') ";

Answer 1

自去年以來發生了很多事情。在這里，我試圖簡化答案。

string ConnStr = System.Configuration.ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
string SQL1 = "INSERT INTO tbl_cust(cust_id,cust_name) values ('000001','YoungMcD') ";
string SQL2 = "UPDATE tbl_cust SET custname='OldMcDonald' WHERE cust_id='000001'";

using (SqlConnection conn = new SqlConnection(ConnStr))
{
    SqlTransaction transaction = null;
    try
    {
        conn.Open();
        transaction = conn.BeginTransaction();
        using (SqlCommand cmd = new SqlCommand(SQL1, conn, transaction)) { cmd.ExecuteNonQuery(); }
        using (SqlCommand cmd = new SqlCommand(SQL2, conn, transaction)) { cmd.ExecuteNonQuery(); }
        transaction.Commit();
        savestats = true;
    }
    catch (Exception ex)
    {
         // Attempt to roll back the transaction.
        try
        {
            transaction.Rollback();
        }
        catch (Exception ex2)
        {
            // This catch block will handle any errors that may have occurred
            // on the server that would cause the rollback to fail, such as
            // a closed connection.
        }
    }
}

之所以在try{}之外聲明事務，是因為我們可以在catch{}回滾它。

這段代碼的conn.Open()是，無論什么原因在conn.Open()發生錯誤，然后嘗試進行transaction.Rollback() conn.Open() transaction.Rollback()將導致異常。

這就是為什么要添加另一個try{} catch{}來處理它的原因。

Answer 2

您應該使用一個命令，並將連接包裝在“使用”塊中，以便正確處理它。 另外，在執行事務提交后，您應該通過執行SqlDataReader從tbl_supplier中進行讀取。 我假設您只是想知道提交事務后受影響的行數。

這是代碼的簡化版本。

var conn = System.Configuration.ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
string SQL1 = "INSERT INTO tbl_cust(cust_id,cust_name) values ('000001','YoungMcD') ";
string SQL2 = "UPDATE tbl_cust SET custname='OldMcDonald' WHERE cust_id='000001'";

using (SqlConnection connection = new SqlConnection(conn))
{
    connection.Open();
    SqlTransaction sqlTran = connection.BeginTransaction();
    SqlCommand command = connection.CreateCommand();
    command.Transaction = sqlTran;

    try
    {
        command.CommandText = SQL1;
        int rowsAffected = command.ExecuteNonQuery();
        command.CommandText = SQL2;
        rowsAffected += command.ExecuteNonQuery();
        transaction.Commit();
    }
    catch (Exception ex1)
    {
        // Attempt to roll back the transaction.
        try
        {
            transaction.Rollback();
        }
        catch (Exception ex2)
        {
            // This catch block will handle any errors that may have occurred
            // on the server that would cause the rollback to fail, such as
            // a closed connection.
        }
    }
}