vb.net 如果某个列值等于某值，则获取行索引
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Get row index if some column value is equal to something
提问by user1570048
In this datatable there are no duplicates, I need the row index where column x value equals 2. I would do it like this:
在此数据表中没有重复项，我需要列 x 值等于 2 的行索引。我会这样做：
Dim rowIndex As Integer = 0
For i = 0 To mtable.Rows.Count - 1
If mtable.Rows(i)("x") = 2 Then
rowIndex = i
Exit For
End If
Next
I will be calling this process multiple times per second. Is there a faster way to do this in .NET?
我将每秒多次调用此过程。在 .NET 中是否有更快的方法来做到这一点？
采纳答案by Andrew Morton
Multiple times per second is a bit vague - tens or thousands?
每秒多次有点模糊 - 数万或数千？
You could create a hash table mapping the value of "x" to the row number:
您可以创建一个哈希表，将“x”的值映射到行号：
Dim nLookups = mtable.Rows.Count - 1
Dim lookupHash As New Hashtable(nLookups)
For i = 0 To nLookups
lookupHash.Add(CInt(mtable.Rows(i)("x")), i)
Next
then
然后
Dim rowSought As Integer = -1
If lookupHash.ContainsKey(2) Then
rowSought = lookupHash(2)
End If
Or if the range of possible values of "x" is suitable, you could use an array to map the value to the row number.
或者，如果“x”的可能值范围合适，您可以使用数组将值映射到行号。
回答by DotNetUser
DataTable select could work, i think it should be faster than iterating over the collection of rows.
DataTable select 可以工作，我认为它应该比迭代行集合更快。
var index = mtable.Rows.IndexOf(mtable.Select("x = 2").FirstOrDefault());
