我们有一个对象(XML 或 JSON)并且我们成功地将它映射到一个 DTO，它需要很长时间(5~7 分钟)才能插入到我们的数据库中，所以我们通过 Parallel.ForEach，但最终，我们注意到有一些数据输入不正确，比如 Category 包含所有同名的项目，但其他不同的属性是 100% 正确的，在其他情况下，我们注意到所有数据在一个类别中都是相同的，尽管提供的 JSON 对象没有那个。
我承认它是如此之快，不到一分钟，但插入错误，请看下面使用的代码:
JSON
[
{
"CategoryId": 1,
"CategoryName": "Drinks",
"SortOrder": 1,
"Products": [
{
"ProductId": 100,
"ProductName": "Black Tea",
"SortOrder": 1,
"Price": 5,
"Choices": []
},
{
"ProductId": 101,
"ProductName": "Turkish Coffee",
"SortOrder": 2,
"Price": 7.5,
"Choices": []
},
{
"ProductId": 102,
"ProductName": "Green Tea",
"SortOrder": 3,
"Price": 6,
"Choices": []
},
{
"ProductId": 103,
"ProductName": "Café Latte Medium",
"SortOrder": 4,
"Price": 10,
"Choices": []
},
{
"ProductId": 104,
"ProductName": "Orange Juice",
"SortOrder": 5,
"Price": 11,
"Choices": []
},
{
"ProductId": 105,
"ProductName": "Mixed Berry Juice",
"SortOrder": 6,
"Price": 12.5,
"Choices": []
}
]
},
{
"CategoryId": 1,
"CategoryName": "Meals",
"SortOrder": 1,
"Products": [
{
"ProductId": 200,
"ProductName": "Breakfast Meal",
"SortOrder": 1,
"Price": 16,
"Choices": [
{
"ChoiceId": 3000,
"ChoiceName": "Strawberry Jam",
"SortOrder": 1,
"Price": 0
},
{
"ChoiceId": 3001,
"ChoiceName": "Apricot Jam",
"SortOrder": 2,
"Price": 0
},
{
"ChoiceId": 3002,
"ChoiceName": "Orange Jam",
"SortOrder": 3,
"Price": 0
},
{
"ChoiceId": 3003,
"ChoiceName": "Café Latte",
"SortOrder": 4,
"Price": 2
}
]
},
{
"ProductId": 201,
"ProductName": "Mixed Grill",
"SortOrder": 1,
"Price": 30,
"Choices": [
{
"ChoiceId": 3004,
"ChoiceName": "Moutabal",
"SortOrder": 1,
"Price": 0
},
{
"ChoiceId": 3005,
"ChoiceName": "Mineral Water",
"SortOrder": 2,
"Price": 0
},
{
"ChoiceId": 3006,
"ChoiceName": "French Fries",
"SortOrder": 2,
"Price": 0
},
{
"ChoiceId": 3007,
"ChoiceName": "Grilled Potatoes",
"SortOrder": 2,
"Price": 0
}
]
}
]
}
]
C#代码
Parallel.ForEach(categories, (category) =>
{
var newCreatedCategoryId = 0;
using (var connection = new SqlConnection("CONNECTION_STRING_HERE"))
{
connection.Open();
using (var command = new SqlCommand("SP_INSERT_INTO_CATEGORIES", connection))
{
command.CommandType = CommandType.StoredProcedure;
command.Parameters.AddWithValue("@P1", category.CategoryName);
command.Parameters.AddWithValue("@P2", category.SortOrder);
newCreatedCategoryId = int.Parse(command.ExecuteScalar().ToString());
command.Dispose();
}
connection.Close();
}
if (newCreatedCategoryId > 0)
{
Parallel.ForEach(category.Products, (product) =>
{
using (var connection = new SqlConnection("CONNECTION_STRING_HERE"))
{
connection.Open();
using (var command = new SqlCommand("SP_INSERT_INTO_PRODUCTS", connection))
{
command.CommandType = CommandType.StoredProcedure;
command.Parameters.AddWithValue("@P1", product.ProductName);
command.Parameters.AddWithValue("@P2", product.Price);
command.Parameters.AddWithValue("@P3", product.SortOrder);
command.Parameters.AddWithValue("@P4", newCreatedCategoryId);
command.ExecuteNonQuery();
command.Dispose();
}
connection.Close();
}
});
}
});
我看了here ，但这不是我们的问题，我们已经在使用 SCOPE_IDENTITY() 来获取当前执行范围内最后生成的身份。
另一方面，即使没有 TableLock，也不允许使用 SqlBulkCopy 插入此数量的数据。
最佳答案
问题出在 newCreatedCategoryId 上，让我困惑的是你为什么调用 newCreatedCategoryId = int.Parse(command.ExecuteScalar().ToString()); 再次在内循环中。我的意思是，如果它只是类别的 id，则不需要再次递增。
看看下面的编辑。您最好将第二个 Parallel.ForEach 放入标准 foreach 我的意思是无论如何这都是并行工作的。最后，Parallel.ForEach 并不真正适合 IO 任务，正确的模式是异步和等待。说您可能会使用 TPL 数据流中的 ActionBlock 来充分利用两全其美的优势。看看我回答的这个问题中的数据流示例 Downloading 1,000+ files fast?
Parallel.ForEach(categories, (category) =>
{
var newCreatedCategoryId = 0;
using (var connection = new SqlConnection("CONNECTION_STRING_HERE"))
{
connection.Open();
using (var command = new SqlCommand("SP_INSERT_INTO_CATEGORIES", connection))
{
command.CommandType = CommandType.StoredProcedure;
command.Parameters.AddWithValue("@P1", category.CategoryName);
command.Parameters.AddWithValue("@P2", category.SortOrder);
newCreatedCategoryId = int.Parse(command.ExecuteScalar().ToString());
command.Dispose();
}
connection.Close();
}
if (newCreatedCategoryId > 0)
{
foreach(product in category.Products)
{
using (var connection = new SqlConnection("CONNECTION_STRING_HERE"))
{
connection.Open();
using (var command = new SqlCommand("SP_INSERT_INTO_PRODUCTS", connection))
{
command.CommandType = CommandType.StoredProcedure;
command.Parameters.AddWithValue("@P1", product.ProductName);
command.Parameters.AddWithValue("@P2", product.Price);
command.Parameters.AddWithValue("@P3", product.SortOrder);
command.Parameters.AddWithValue("@P4", newCreatedCategoryId);
command.Dispose();
}
connection.Close();
}
}//);
}
});
关于插入 SQL 数据库时 C# 嵌套 Parallel.ForEach，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51057355/