如何优化嵌套的foreach循环 [英] How do I optimize nested foreach loops

问题描述

我有两个foreach循环。其他循环中的一个Foreach。我如何优化那些嵌套的foreach循环



我尝试过：

I have two foreach loops. One Foreach in other loop. How do i optimize those nested foreach loops

What I have tried:

foreach (var t in ValidBCodes)
{
     foreach (var y in InsertRows)
     {
          var newRow = ds.Tables["FACT"].NewRow();
          newRow["S_ID"] = DestinationScenarioId;
          newRow["B_ID"] = t;
          newRow["G_ID"] = y["GLOBALFIELD_ID"];
          newRow["AMOUNT"] = y["AMOUNT"];

          ds.Tables["FACT"].Rows.Add(newRow);
      }
}

推荐答案

如果 newRow 无法重复使用，无法进行优化。

如果 newRow 可以重复使用，我会重写代码这样。

If newRow can't be reused, there is no optimization possible.
If newRow can be reused, I would rewrite the code this way.

var newRow = ds.Tables["FACT"].NewRow();
foreach (var y in InsertRows)
{
	newRow["S_ID"] = DestinationScenarioId;
	newRow["G_ID"] = y["GLOBALFIELD_ID"];
	newRow["AMOUNT"] = y["AMOUNT"];
	foreach (var t in ValidBCodes)
	{
		newRow["B_ID"] = t;
		ds.Tables["FACT"].Rows.Add(newRow);
	}
}

[更新]

如果 newRow 无法重复使用，只需交换循环就可以让编译器看到 y [GLOBALFIELD_ID] 和 y [AMOUNT] 在内循环中是常量，并将这些值的读数移到内循环之外。

[update]
If newRow can't be reused, simply swapping the loops allow the compiler to see that y["GLOBALFIELD_ID"] and y["AMOUNT"] are constant in the inner loop and move the reading of these values outside of inner loop.

foreach (var y in InsertRows)
{
     foreach (var t in ValidBCodes)
     {
          var newRow = ds.Tables["FACT"].NewRow();
          newRow["S_ID"] = DestinationScenarioId;
          newRow["B_ID"] = t;
          newRow["G_ID"] = y["GLOBALFIELD_ID"];
          newRow["AMOUNT"] = y["AMOUNT"];
 
          ds.Tables["FACT"].Rows.Add(newRow);
      }
}

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