C# 将多行添加到数据表
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Adding multiple rows to DataTable
提问by Anuj
I know two ways to add new row with data to a DataTable
我知道两种将带有数据的新行添加到 DataTable
string[] arr2 = { "one", "two", "three" };
dtDeptDtl.Columns.Add("Dept_Cd");
for (int a = 0; a < arr2.Length; a++)
{
DataRow dr2 = dtDeptDtl.NewRow();
dr2["Dept_Cd"] = DeptCd[a];
dtDeptDtl.Rows.Add(dr2);
}
for (int a = 0; a < arr2.Length; a++)
{
dtDeptDtl.Rows.Add();
dtDeptDtl.Rows[a]["Dept_Cd"] = DeptCd[a];
}
Both the above methods will give me the same result i.e One Two Three will be added in DataTablein seperate rows.
上述两种方法都会给我相同的结果，即一二三将被添加DataTable到单独的行中。
But my question is that what is the difference between both the steps and which one is better way performance wise?
但我的问题是，这两个步骤之间有什么区别，哪一个更好地提高性能？
采纳答案by Alex Filipovici
Some decompiler observations
一些反编译器观察
In both scenarios, a different overload of the System.Data.DataRowCollection.Addmethod is being used.
在这两种情况下，都使用了不同的System.Data.DataRowCollection.Add方法重载。
The first approach uses:
第一种方法使用：
public void Add(DataRow row)
{
this.table.AddRow(row, -1);
}
The second approach will use:
第二种方法将使用：
public DataRow Add(params object[] values)
{
int record = this.table.NewRecordFromArray(values);
DataRow dataRow = this.table.NewRow(record);
this.table.AddRow(dataRow, -1);
return dataRow;
}
Now, take a look at this little beast:
现在，看看这个小野兽：
internal int NewRecordFromArray(object[] value)
{
int count = this.columnCollection.Count;
if (count < value.Length)
{
throw ExceptionBuilder.ValueArrayLength();
}
int num = this.recordManager.NewRecordBase();
int result;
try
{
for (int i = 0; i < value.Length; i++)
{
if (value[i] != null)
{
this.columnCollection[i][num] = value[i];
}
else
{
this.columnCollection[i].Init(num);
}
}
for (int j = value.Length; j < count; j++)
{
this.columnCollection[j].Init(num);
}
result = num;
}
catch (Exception e)
{
if (ADP.IsCatchableOrSecurityExceptionType(e))
{
this.FreeRecord(ref num);
}
throw;
}
return result;
}
Especially, note the this.columnCollection[i][num] = value[i];, which will call:
尤其要注意this.columnCollection[i][num] = value[i];, 它将调用：
public DataColumn this[int index]
{
get
{
DataColumn result;
try
{
result = (DataColumn)this._list[index];
}
catch (ArgumentOutOfRangeException)
{
throw ExceptionBuilder.ColumnOutOfRange(index);
}
return result;
}
}
Moving forward, we discover that actually _listis an ArrayList:
继续前进，我们发现实际上_list是一个ArrayList：
private readonly ArrayList _list = new ArrayList();
Conclusion
结论
In order to summarize the above, if you are using dtDeptDtl.Rows.Add();instead of dtDeptDtl.Rows.Add(dr2);, you will get a performance degradationwhich will increase exponentially, as the number of columns grows. The responsible line for the degradation is call to the NewRecordFromArraymethod, which iterates over an ArrayList.
为了总结以上内容，如果您使用的是dtDeptDtl.Rows.Add();而不是dtDeptDtl.Rows.Add(dr2);，则会导致性能下降，随着列数的增加，该性能将呈指数增长。负责降级的行是对NewRecordFromArray方法的调用，该方法迭代ArrayList.
Note: This can be easily tested if you add, let's say, 8 columns to the table and make some tests in a forlooping 1000000 times.
注意：如果您向表中添加 8 列并在for循环 1000000 次中进行一些测试，则可以轻松测试。
