PowerShell从文本文件导入数据到二维数组时遇空数组索引错误求助

Hey there! Since you're coming from Java and new to PowerShell, let's break down why you're hitting that error and get your CSV-like text file into a proper 2D array.

Why the Error Happens #

Your initial code has two key issues:

• Incorrect array initialization: $array = @(), @() creates an array that contains two empty sub-arrays. When your loop reaches the 3rd line ($i=2), $array[$i] doesn't exist—it's null, hence the "Cannot index into a null array" error.
• Fixed-size array limitation: Even for the first two lines, PowerShell's standard arrays are fixed-size. You can't directly assign to $array[$i][$j] because the sub-array is empty and has no slot at index $j yet.

Correct Ways to Create the 2D Array #

Method 1: Simple Fixed-Size Array (Good for Small Files) #

This approach builds the 2D array by adding each split row as a single element to the main array:

# Read the file content
$file = Get-Content "C:\Users\UserName\Desktop\sqlServers.txt"
# Initialize an empty main array
$array = @()

foreach ($line in $file) {
    # Split the line into a string array
    $row = $line.Split(",")
    # Add the row to the main array (the leading comma ensures it's added as a single sub-array)
    $array += ,$row
}

# Test accessing elements
Write-Host "First row, second element: $($array[0][1])"

Note the leading comma ,$row—this tells PowerShell to add the entire row array as one element instead of expanding its elements into the main array (which would turn it into a 1D array).

Method 2: Dynamic ArrayList (Better for Large Files) #

If you're working with a large file, ArrayList is more efficient than using += (which recreates the entire array each time):

$file = Get-Content "C:\Users\UserName\Desktop\sqlServers.txt"
# Initialize a dynamic array list
$array = New-Object System.Collections.ArrayList

foreach ($line in $file) {
    $row = $line.Split(",")
    # Add the row to the list ( [void] suppresses the index number output from Add() )
    [void]$array.Add($row)
}

# Test accessing elements
Write-Host "Third row, fourth element: $($array[2][3])"

Bonus: Use PowerShell's Built-in CSV Support #

If you later want to work with this data as structured objects (similar to Java POJOs) instead of a raw 2D array, PowerShell's Import-Csv cmdlet is perfect:

# Define headers for your data columns
$headers = "Version", "ReservedValue", "CU", "BuildNumber", "Edition", "Flag"
# Import the file as a collection of objects
$sqlServerObjects = Import-Csv "C:\Users\UserName\Desktop\sqlServers.txt" -Header $headers

# Access properties like objects
Write-Host "First entry's edition: $($sqlServerObjects[0].Edition)"

内容的提问来源于stack exchange，提问作者Brenden Laible