Reduce allocation in DownloadTimeoutStream.ReadAsync caused by avoidable string formatting/allocations (#7035)

nareshjo · Naresh Joshi · web-flow · commit a0bfa977eee0 · 2026-01-09T14:34:37.000-08:00
Co-authored-by: Naresh Joshi &lt;Naresh.Joshi@microsoft.com&gt;
diff --git a/src/NuGet.Core/NuGet.Protocol/Utility/DownloadTimeoutStream.cs b/src/NuGet.Core/NuGet.Protocol/Utility/DownloadTimeoutStream.cs
@@ -71,12 +71,6 @@ public override async Task<int> ReadAsync(
             int count,
             CancellationToken cancellationToken)
         {
-            var timeoutMessage = string.Format(
-                CultureInfo.CurrentCulture,
-                Strings.Error_DownloadTimeout,
-                _downloadName,
-                _timeout.TotalMilliseconds);
-
             try
             {
                 var result = await TimeoutUtility.StartWithTimeout(
@@ -89,6 +83,12 @@ public override async Task<int> ReadAsync(
             }
             catch (TimeoutException e)
             {
+                var timeoutMessage = string.Format(
+                    CultureInfo.CurrentCulture,
+                    Strings.Error_DownloadTimeout,
+                    _downloadName,
+                    _timeout.TotalMilliseconds);
+
                 // Failed stream operations should throw an IOException.
                 throw new IOException(timeoutMessage, e);
             }

Original file line number	Diff line number	Diff line change
`@@ -71,12 +71,6 @@ public override async Task<int> ReadAsync(`
`71`	`71`	`int count,`
`72`	`72`	`CancellationToken cancellationToken)`
`73`	`73`	`{`
`74`		`- var timeoutMessage = string.Format(`
`75`		`- CultureInfo.CurrentCulture,`
`76`		`- Strings.Error_DownloadTimeout,`
`77`		`- _downloadName,`
`78`		`- _timeout.TotalMilliseconds);`
`79`		`-`
`80`	`74`	`try`
`81`	`75`	`{`
`82`	`76`	`var result = await TimeoutUtility.StartWithTimeout(`
`@@ -89,6 +83,12 @@ public override async Task<int> ReadAsync(`
`89`	`83`	`}`
`90`	`84`	`catch (TimeoutException e)`
`91`	`85`	`{`
	`86`	`+ var timeoutMessage = string.Format(`
	`87`	`+ CultureInfo.CurrentCulture,`
	`88`	`+ Strings.Error_DownloadTimeout,`
	`89`	`+ _downloadName,`
	`90`	`+ _timeout.TotalMilliseconds);`
	`91`	`+`
`92`	`92`	`// Failed stream operations should throw an IOException.`
`93`	`93`	`throw new IOException(timeoutMessage, e);`
`94`	`94`	`}`