📘 Power Automate Blog Post: Extract Library Name and Library ID from "When a file is created (properties only)" Trigger

In this guide, we’ll walk through building a robust Power Automate flow that:

• Works with the “When a file is created (properties only)” trigger.

• Dynamically extracts both Library Name and Library ID (GUID).

• Avoids unreliable URL parsing.

• Uses SharePoint REST API for accurate library details.

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🎯 Scenario

You want a flow that triggers automatically when a new file is uploaded to any SharePoint document library and retrieves:

• The correct Library Name.

• The accurate Library ID (GUID).

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🔹 Full Step-by-Step Solution

1️⃣ Trigger: "When a file is created (properties only)"

• Configure:

  • Site Address: Your SharePoint site.

  • Library Name: Specify a library or leave blank for all libraries.

This trigger provides metadata such as:

• {Link} (file URL)

• {Path} (relative path)

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2️⃣ Compose: File URL

• Name: Compose_FileURL

• Expression:

  triggerOutputs()?['body/{Link}']
  

✅ Captures the full file URL.

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3️⃣ Compose: Relative Path

• Name: Compose_RelativePath

• Expression:

  triggerOutputs()?['body/{Path}']
  

✅ Retrieves the relative path like LibraryName/folder/file.docx.

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4️⃣ Compose: Library Name

• Name: Compose_LibraryName

• Expression:

  first(split(outputs('Compose_RelativePath'), '/'))
  

✅ Dynamically extracts the first segment of the path as the library name.

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5️⃣ Send an HTTP request to SharePoint

• Action: Send an HTTP request to SharePoint

• Site Address: Same site as trigger.

• Method: GET

• URI:

  _api/web/lists/getByTitle('@{outputs('Compose_LibraryName')}')?$select=Id,Title
  

✅ Dynamically retrieves Library metadata by name.

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6️⃣ Parse JSON: Parse HTTP response

• Content:

  Body from HTTP request
  

• Schema:

  {
    "type": "object",
    "properties": {
      "d": {
        "type": "object",
        "properties": {
          "Id": { "type": "string" },
          "Title": { "type": "string" }
        }
      }
    }
  }
  

✅ Parses the response to easily access Id and Title fields.

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7️⃣ Compose: Library ID

• Name: Compose_LibraryID

• Expression:

  outputs('Parse_JSON')?['d']?['Id']
  

✅ Extracts the correct Library ID (GUID) from the parsed JSON response.

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🔔 Key Benefits

• No hardcoding of library names or IDs.

• Works for any document library dynamically.

• Reliable and API-driven.

• Avoids fragile parsing of URL query strings.

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🔹 Summary of Key Expressions

Step	Expression
Compose_FileURL	triggerOutputs()?['body/{Link}']
Compose_RelativePath	triggerOutputs()?['body/{Path}']
Compose_LibraryName	first(split(outputs('Compose_RelativePath'), '/'))
Compose_LibraryID	outputs('Parse_JSON')?['d']?['Id']

✅ This solution ensures your Power Automate flow is dynamic, reliable, and production-ready when working with the “When a file is created” trigger in SharePoint.

👉 Want this packaged as a ready-to-import .zip template? Just ask! 👍