遍历哈希表中的日期？

Question

我在 Powershell 中有一个如下所示的哈希表 ($hash_dates.GetEnumerator() | sort -Property name)：

11/1/2016 12:00:00 AM          5
11/2/2016 12:00:00 AM          3
11/4/2016 12:00:00 AM          2

密钥的类型为 DateTime。

我正在运行一个 for 循环来捕获所有日期（仅限日期，时间无关紧要，因此整个午夜）并根据日期提取哈希表中的每个值。代码：

$startdate = (get-date).AddDays(-30)
$today = get-date -format G
for($i = $startdate; $i -lt $today; $i=$i.AddDays(1))
{
   $z = $i -split " "
   $z = [datetime]$z[0]
   $z = Get-Date $z -format G
   "Comparing $z to: "
   $hash_dates.Keys | ? { $hash_dates[$_] -eq $z }
}

我使用了-format G 和split 来确保格式匹配。但是循环永远找不到任何结果（即使它循环到 2016 年 11 月 1 日等）。我错过了什么吗？

Answer 1

由于您的哈希表键是[datetime] 对象，因此根本不需要使用日期字符串和字符串解析： p>

$today = (Get-Date).Date # Note the .Date part, which omits the time portion
$startdate = $today.AddDays(-30)

# Note the change from -lt to -le to include today
for($i = $startdate; $i -le $today; $i = $i.AddDays(1))
{
  # Note that `echo` is an alias for `Write-Output`, which is the default,
  # so no need for an explicit output command.
  "Looking for $i..." 
  # Simply try to access the hashtable with $i as the key, which
  # either outputs nothing ($null), or outputs the value for that key.
  $hash_dates.$i
}

Re echo / Write-Output / 默认输出：请注意，您的状态消息将成为您的数据（输出）流，这可能是不受欢迎的。
考虑改用Write-Information。

---

这里有一个简化的解决方案，展示了 PowerShell 的表现力：

$today = (get-date).Date

# Construct an array with all dates of interest.
$dates = -30..0 | % { $today.AddDays($_) } # % is a built-in alias for ForEach-Object

# Pass the entire array as the hashtable "subscript", which returns
# the values for all matching keys while ignoring keys that don't exist.
$hash_dates[$dates]

Answer 2

这是你想要的吗？

$startdate = (get-date).AddDays(-30)
$today = get-date -format G
for($i = $startdate; $i -lt $today; $i=$i.AddDays(1))
{
   $z = $i -split " "
   $z = [datetime]$z[0]
   Echo "Comparing $z to: "
   $z = Get-Date $z
   $hash_dates.$z

}