Powershell：字符串被多次添加到另一个字符串

Question

在构建文本 blob 的脚本中，有一点可以将 "summary" 文本块添加到所述 blob。

虽然脚本只生成一次摘要文本，但它会多次添加到文本 blob 中。

这是 PowerShell 脚本：

#
# Test_TextAppend.ps1
#

$reportMessage = "Body of Report Able Was I Ere I Saw Elba";   # build "report" text

$fruitList = [System.Collections.ArrayList]@();
$vegetableList = [System.Collections.ArrayList]@();

[void]$fruitList.Add("apple");

# Generate a "summary" that includes the contents of both lists
function GenerateSummary()
{
    [System.Text.StringBuilder]$sumText = New-Object ("System.Text.StringBuilder")
    $nameArray = $null;
    [string]$nameList = $null;

    if ($fruitList.Count -gt 0)
    {
        $nameArray = $fruitList.ToArray([System.String]);
        $nameList = [string]::Join(", ", $nameArray);
        $sumText.AppendFormat("The following fruits were found: {0}`n",
            $nameList);
    }

    if ($vegetableList.Count -gt 0)
    {
        $nameArray = $vegetableList.ToArray([System.String]);
        $nameList = [string]::Join(", ", $nameArray);
        $sumText.AppendFormat("The following vegetables were found: {0}`n",
            $nameList);
    }

    if ($sumText.Length -gt 0)
    {
        $sumText.Append("`n");
    }

    return ($sumText.ToString());
}

[string]$summary = (GenerateSummary);

if (![string]::IsNullOrEmpty($summary))    # if there is any "summary" text, prepend it
{
    $reportMessage = $summary + $reportMessage;
}

Write-Output $reportMessage

这是运行时的结果：

The following fruits were found: apple

 The following fruits were found: apple

 The following fruits were found: apple

Body of Report Able Was I Ere I Saw Elba

我使用了代码块而不是 blockquote，因为固定宽度的字体显示了额外的前导空格。

问题：为什么摘要文本重复了三次而不是只重复了一次？

Answer 1

阅读about_Return:

LONG DESCRIPTION

The Return keyword exits a function, script, or script block. It can be used to exit a scope at a specific point, to return a value, or to indicate that the end of the scope has been reached.

Users who are familiar with languages like C or C# might want to use the Return keyword to make the logic of leaving a scope explicit.

In Windows PowerShell, the results of each statement are returned as output, even without a statement that contains the Return keyword. Languages like C or C# return only the value or values that are specified by the Return keyword.

接下来所有三个语句的结果构成函数的输出：

    $sumText.AppendFormat("The following fruits were found: {0}`n", $nameList); 

    $sumText.Append("`n");

return ($sumText.ToString());

（如果 $vegetableList.Count -gt 0 也来自下一条语句）：

$sumText.AppendFormat("The following vegetables were found: {0}`n", $nameList);

Powershell：字符串被多次添加到另一个字符串

Powershell: String is added more than once to another string

string

powershell

stringbuilder

string-concatenation