Fix ItemWithPath throwing on null/empty/whitespace path instead of generating malformed URLs

[Copilot]

• Explore current state of source and test files
• Extract duplicated validation logic into NormalizePathOrThrow private helper
• Fix missing StringComparison.Ordinal in second overload's StartsWith
• Update tests to also assert ParamName == "path" on thrown exceptions
• Run tests to validate changes (22/22 passed)
• Run parallel validation

Original prompt

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This section details on the original issue you should resolve

<issue_title>SDK URL Construction Bug with Empty Filenames</issue_title>
<issue_description>During testing of empty filename scenarios, we discovered a bug in the Microsoft Graph .NET SDK's URL construction when using [ItemWithPath("")]with empty strings.

When calling [graphClient.Drives[driveId].Root.ItemWithPath("").Content.GetAsync()] the SDK generates malformed URLs that duplicate path segments:

GET https://graph.microsoft.com/v1.0/drives/{driveId}/root:443/v1.0/drives/{driveId}/root:/content HTTP/2.0

This issue stems from the [ItemWithPath] extension method in DriveItemRequestBuilderExtensions.cs
builder.Path += $":{path}:"; // When path is "", this becomes "::"

Exected behavior:
https://graph.microsoft.com/v1.0/drives/{driveId}/root::/content
and the SDK should probably return an exception for null filenames

How to repro:

Create a GraphServiceClient instance
Call [graphClient.Drives[driveId].Root.ItemWithPath("").Content.GetAsync()])
Observe the generated HTTP request URL in network logs

SDK version: 5.94.0

Debug output:

HTTP REQUEST >>>>>>>>
------ JWT payload (relevant ID claims only) ------
"app_displayname": DAMS vNext SPE
"appid": 2b376c51-fcaf-4c86-823a-622ecc45c27e
"aud": https://graph.microsoft.com/
"idtyp": app
"iss": https://sts.windows.net/0f7c36b4-4e13-46ce-a1ea-7e6ecb8dd391/
"oid": 81c7703e-f477-4459-a491-235266b06df1
"sub": 81c7703e-f477-4459-a491-235266b06df1
"tid": 0f7c36b4-4e13-46ce-a1ea-7e6ecb8dd391
------ JWT payload (relevant ID claims only) ------

GET https://graph.microsoft.com/v1.0/drives/{driveId}/root:443/v1.0/drives/{driveId}/root:/content HTTP/2.0
Accept: application/octet-stream, application/json
Authorization: REDACTED
Cache-Control: no-store, no-cache
client-request-id: 6e8f0db8-bade-4886-b22f-e98b7f2bc06f
FeatureFlag: 00000003
SdkVersion: graph-dotnet-core/3.2.4 (featureUsage=00000003; hostOS=Microsoft Windows NT 10.0.22631.0; hostArch=X64; runtimeEnvironment=.NET 10.0.0-rc.2.25502.107;)
User-Agent: kiota-dotnet/1.17.1

[no content]

[2025-10-24T21:43:14.2060635+00:00]: Sending request... completed in 53ms [2025-10-24T21:43:14.2599208+00:00].

<<<<<<<< HTTP RESPONSE <<<<<<<<
HTTP/2.0 400 Bad Request
client-request-id: 6e8f0db8-bade-4886-b22f-e98b7f2bc06f
Content-Type: application/json
Date: Fri, 24 Oct 2025 21:43:13 GMT
request-id: c83d5fd8-1a6f-4a1c-b330-8e720631c89b
Strict-Transport-Security: max-age=31536000
x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"East US","Slice":"E","Ring":"5","ScaleUnit":"000","RoleInstance":"BL6PEPF0002814A"}}

{
"error": {
"code": "BadRequest",
"message": "Resource not found for the segment \u0027root:443\u0027.",
"innerError": {
"date": "2025-10-24T21:43:14",
"request-id": "c83d5fd8-1a6f-4a1c-b330-8e720631c89b",
"client-request-id": "6e8f0db8-bade-4886-b22f-e98b7f2bc06f"
}
}
}</issue_description>

Comments on the Issue (you are @copilot in this section)

@lramosvea The extension method should return an argument null exception is the string provided is null and argument exception when the string provided is empty or white space.

• Fixes SDK URL Construction Bug with Empty Filenames #3023

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR makes ItemWithPath fail fast for invalid path inputs to prevent malformed Microsoft Graph URLs when null, empty, or whitespace strings are provided.

Changes:

• Added argument validation to both ItemWithPath overloads (RootRequestBuilder and DriveItemItemRequestBuilder).
• Added unit tests covering null, empty, and whitespace path inputs for both overloads.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
tests/Microsoft.Graph.DotnetCore.Test/Requests/Extensions/DriveItemRequestBuilderExtensionsTests.cs	Adds test coverage for invalid path inputs on both ItemWithPath overloads.
src/Microsoft.Graph/Extensions/DriveItemRequestBuilderExtensions.cs	Adds null + empty/whitespace validation and normalizes missing leading / for path.