使用scope_Identity（）檢索最后插入的ID

Question

我正在嘗試使用SCOPE_IDENTITY插入最后一個ID，但出現錯誤。 我將SQL Server 2012與Visual Studio Express 2013一起使用

這是我的代碼

protected void PerformInscription(string sEmail, string sPassword,string sName)
{
    bool buserIdAuthenticated = false;
    string salt = null;
    string passwordHash = pwdManager.GeneratePasswordHash(txtPassword.Text, out salt);

    SqlConnection sqlConnection;
    sqlConnection = new SqlConnection();

    try
    {
        sqlConnection.ConnectionString = sqlDataSource1.ConnectionString;

        string insertStatement = "INSERT INTO [User] "
                                 + "(email, hash, salt, name) "
                                 + "VALUES (@email, @hash, @salt, @name);"
                                 + "SELECT SCOPE_IDENTITY() AS id_user;";

        SqlCommand insertCommand = new SqlCommand(insertStatement, sqlConnection);

        insertCommand.Parameters.Add("@email", SqlDbType.VarChar, 50).Value = sEmail;
        insertCommand.Parameters.Add("@hash", SqlDbType.VarChar, 50).Value = passwordHash;
        insertCommand.Parameters.Add("@salt", SqlDbType.VarChar, 50).Value = salt;
        insertCommand.Parameters.Add("@nom", SqlDbType.VarChar, 50).Value = sName;

        sqlConnection.Open();

        int count = insertCommand.ExecuteNonQuery();

        int User_ID = Convert.ToInt32(insertCommand.Parameters["@id_user"].Value);
        Session["Id_user"] = User_ID;

        insertCommand.Dispose();

        if (count >= 1)
        {
            buserIdAuthenticated = true;                    
            Session["userIdAuthenticated"] = buserIdAuthenticated;
            Response.Redirect("../pages/Welcome.aspx");
        }
    }

    catch (SqlException ex)
    {
        lblMessage.Text = ex.Message;
    }

    finally
    {
        sqlConnection.Close();
    }
  }
}

我想捕獲最后一個被定義為自動增量身份的user_id。

這是我得到的錯誤

System.Data.dll中發生類型'System.IndexOutOfRangeException'的異常，但未在用戶代碼中處理。

附加信息：此SqlParameterCollection不包含帶有ParameterName'@id_user'的SqlParameter。

我決定拆分兩個請求。 1個插入和1個選擇

    SqlConnection sqlConnection;
    sqlConnection = new SqlConnection();

    try
    {
        sqlConnection.ConnectionString = sqlDataSource1.ConnectionString;

        string insertStatement = "INSERT INTO [User] "
                                 + "(email, hash, salt, name) "
                                 + "VALUES (@email, @hash, @salt, @name)";

        SqlCommand insertCommand = new SqlCommand(insertStatement, sqlConnection);

        insertCommand.Parameters.Add("@email", SqlDbType.VarChar, 50).Value = sEmail;
        insertCommand.Parameters.Add("@hash", SqlDbType.VarChar, 50).Value = passwordHash;
        insertCommand.Parameters.Add("@salt", SqlDbType.VarChar, 50).Value = salt;
        insertCommand.Parameters.Add("@name", SqlDbType.VarChar, 50).Value = sName;

        sqlConnection.Open();

        int count = insertCommand.ExecuteNonQuery();

        insertCommand.Dispose();

        if (count >= 1)
        {
            string selectStatement = "SELECT SCOPE_IDENTITY() AS id_user";
            SqlCommand selectCommand = new SqlCommand(selectStatement, sqlConnection);
            selectCommand.Parameters.Add("@Id_user", SqlDbType.Int, 0, "Id_user");
            int newID = (int)selectCommand.ExecuteScalar();

            int User_ID = Convert.ToInt32(selectCommand.Parameters["@Id_user"].Value);
            Session["Id_user"] = User_ID;

            buserIdAuthenticated = true;                   
            Session["userIdAuthenticated"] = buserIdAuthenticated;
            Response.Redirect("../pages/Bienvenue.aspx");
        }
    }

    catch (SqlException ex)
    {
        lblMessage.Text = ex.Message;
    }

    finally
    {
        sqlConnection.Close();
    }
  }
 }

Answer 1

您不應將查詢分為兩個查詢。 您應該在插入查詢中選擇/設置結果。

我為您提供了一個示例：

第一種方法是使用select返回單個值

private void Method1()
{
    string sEmail = "test@test.com";
    string passwordHash = "#$@#$@!#@$$@#!#@$!#@$!";
    string salt = "????";
    string sName = "John";

    using (SqlConnection sqlConnection = new SqlConnection(_connectionString))
        try
        {
            sqlConnection.Open();

            string insertStatement = "INSERT INTO [User] "
                                        + "(email, hash, salt, name) "
                                        + "VALUES (@email, @hash, @salt, @name)"

                                        + "SELECT SCOPE_IDENTITY()";

            using (SqlCommand insertCommand = new SqlCommand(insertStatement, sqlConnection))
            {

                insertCommand.Parameters.Add("@email", SqlDbType.VarChar, 50).Value = sEmail;
                insertCommand.Parameters.Add("@hash", SqlDbType.VarChar, 50).Value = passwordHash;
                insertCommand.Parameters.Add("@salt", SqlDbType.VarChar, 50).Value = salt;
                insertCommand.Parameters.Add("@name", SqlDbType.VarChar, 50).Value = sName;


                int userId = Convert.ToInt32(insertCommand.ExecuteScalar());
                Trace.WriteLine("User created with id: " + userId);
            }
        }

        catch (SqlException ex)
        {
            Trace.WriteLine(ex.Message);
            //lblMessage.Text = ex.Message;
        }
}

第二種方法是定義輸出參數，這樣您就可以返回多個值。

private void Method2()
{
    string sEmail = "test@test.com";
    string passwordHash = "#$@#$@!#@$$@#!#@$!#@$!";
    string salt = "????";
    string sName = "John";

    using (SqlConnection sqlConnection = new SqlConnection(_connectionString))
        try
        {
            sqlConnection.Open();

            string insertStatement = "INSERT INTO [User] "
                                        + "(email, hash, salt, name) "
                                        + "VALUES (@email, @hash, @salt, @name)"

                                        + "SET @user_id = SCOPE_IDENTITY()";

            using (SqlCommand insertCommand = new SqlCommand(insertStatement, sqlConnection))
            {

                insertCommand.Parameters.Add("@email", SqlDbType.VarChar, 50).Value = sEmail;
                insertCommand.Parameters.Add("@hash", SqlDbType.VarChar, 50).Value = passwordHash;
                insertCommand.Parameters.Add("@salt", SqlDbType.VarChar, 50).Value = salt;
                insertCommand.Parameters.Add("@name", SqlDbType.VarChar, 50).Value = sName;

                insertCommand.Parameters.Add("@user_id", SqlDbType.Int).Direction = ParameterDirection.Output;

                insertCommand.ExecuteNonQuery();

                int userId = Convert.ToInt32(insertCommand.Parameters["@user_id"].Value);
                Trace.WriteLine("User created with id: " + userId);
            }
        }

        catch (SqlException ex)
        {
            Trace.WriteLine(ex.Message);
            //lblMessage.Text = ex.Message;
        }
}

最好的辦法是，如果查詢是靜態的，請將這些查詢放入存儲過程中。 這樣可以加快查詢速度。

Answer 2

如評論中所述：

string insertStatement = "INSERT INTO [User] "
                                 + "(email, hash, salt, name) "
                                 + "VALUES (@email, @hash, @salt, @name);"
                                 + "SELECT @id_user = SCOPE_IDENTIY();";

應該 ：

string insertStatement = "INSERT INTO [User] "
                                 + "(email, hash, salt, name) "
                                 + "VALUES (@email, @hash, @salt, @name);"
                                 + "SELECT SCOPE_IDENTITY() AS id_user;";

查看SCOPE_IDENTIY和SCOPE_IDENTITY之間的區別。

並注意對SELECT語句語法的更新。