Azure自动化账户RunBook发送带附件邮件报错求助

问题描述 #

在Azure自动化账户中创建RunBook，通过Azure Resource Graph查询资源并导出为CSV文件发送邮件时，出现以下错误：

System.Management.Automation.RuntimeException: You cannot call a method on a null-valued expression.
at CallSite.Target(Closure , CallSite , Object , String )
at System.Dynamic.UpdateDelegates.UpdateAndExecute2[T0,T1,TRet](CallSite site, T0 arg0, T1 arg1)
at System.Management.Automation.Interpreter.DynamicInstruction`3.Run(InterpretedFrame frame)
at System.Management.Automation.Interpreter.EnterTryCatchFinallyInstruction.Run(InterpretedFrame frame)

RunBook代码如下：

$IdentityAccountID = Get-AutomationVariable  -Name "IdentityName"
Connect-AzAccount -Identity -AccountId $IdentityAccountID -Tenant "<tenantName>" -SubscriptionId "1234-1234-1234-1234-1234"

$query = @"
resources
| where type in (
    'microsoft.sql/servers/databases',
    'microsoft.web/serverfarms'
)
| join kind=inner (
    resourcecontainers
    | where type =~ 'microsoft.resources/subscriptions'
    | project subscriptionId, subscriptionName=name
) on subscriptionId
| where subscriptionId in (
  '1234-1234-1234-1234-1234',
    '1234-1234-1234-1234-1234',
    '1234-1234-1234-1234-1234'
)
| where name != 'master'
| project subscriptionName, resourceType=type, resourceName=name, sku, resourceGroup
| order by subscriptionName, resourceType, resourceName
"@

#$csvpath = "$env:TEMP\ResourcesInventory.csv"
# Execute the query
$result = Search-AzGraph -Query $query
$result.Data | Export-Csv -Path "$env:TEMP\ResourcesInventory.csv" -Notype

$CredSmtp = Get-AutomationPSCredential -Name "smtpCred" 

# Sender and Recipient Info
$MailFrom = "no-reply@email.com"
$MailTo = "reciever@email.com"

# Sender Credentials
$Username = $CredSmtp.UserName
$Password = $CredSmtp.GetNetworkCredential().Password

$SmtpServer = "smtp.sendgrid.net"
$SmtpPort = "587"

# configure message
$Message.Attachments.Add("$env:TEMP\ResourcesInventory.csv")
$MessageSubject = "Azure resources Inventory Report" 
$Message = New-Object System.Net.Mail.MailMessage $MailFrom, $MailTo
$Message.IsBodyHTML = $true
$Message.Subject = $MessageSubject
$Message.Body = @'
<!DOCTYPE html>
<html>
<head>
</head>
<body>
Hello, 
<p>Please Find attached the resources inventory report regarding the subscriptions assigned to you </p>

Regards
</body>
</html>
'@

# Construct the SMTP client object, credentials, and send
$Smtp = New-Object Net.Mail.SmtpClient($SmtpServer,$SmtpPort)
$Smtp.EnableSsl = $true
$Smtp.Credentials = New-Object System.Net.NetworkCredential($Username,$Password)
$Smtp.Send($Message)

问题原因及修复方案 #

1. 邮件对象初始化顺序错误 #

报错的直接原因是代码先调用$Message.Attachments.Add()，但此时$Message变量还未创建，属于对Null对象调用方法。

修复：
调整代码顺序，先创建$Message对象，再添加附件：

# configure message
$MessageSubject = "Azure resources Inventory Report" 
$Message = New-Object System.Net.Mail.MailMessage $MailFrom, $MailTo
# 先创建对象，再添加附件
$Message.Attachments.Add("$env:TEMP\ResourcesInventory.csv")
$Message.IsBodyHTML = $true
$Message.Subject = $MessageSubject
$Message.Body = @'
<!DOCTYPE html>
<html>
<head>
</head>
<body>
Hello, 
<p>Please Find attached the resources inventory report regarding the subscriptions assigned to you </p>

Regards
</body>
</html>
'@

2. 处理查询结果为空的情况 #

如果Search-AzGraph返回无数据，$result.Data会是Null，执行Export-Csv时会触发报错，需要添加空值判断：

修复：

$result = Search-AzGraph -Query $query
if ($result.Data) {
    $result.Data | Export-Csv -Path "$env:TEMP\ResourcesInventory.csv" -NoTypeInformation
} else {
    Write-Output "No resources found from the query."
    # 可选：修改邮件内容说明无数据
}

3. 验证自动化资源配置 #

• 确认自动化账户中已创建名为IdentityName的变量，值正确对应托管标识的ID
• 确认名为smtpCred的PS凭据已正确配置，包含有效的SMTP用户名和密码

4. 检查CSV文件存在性 #

添加文件存在检查，避免附件路径无效的问题：

$csvPath = "$env:TEMP\ResourcesInventory.csv"
if (Test-Path $csvPath) {
    $Message.Attachments.Add($csvPath)
} else {
    $Message.Body = $Message.Body.Replace("Please Find attached", "No resources report available (no data found)")
}

内容的提问来源于stack exchange，提问作者Brayhan Castro