Analyzing MSBuild Failures with Binary Logs

Use MSBuild's built-in binlog replay to convert binary logs into searchable text logs, then analyze with standard tools (grep , cat , head , tail , find ).

Build Error Investigation (Primary Workflow)

Step 1: Replay the binlog to text logs

Replay produces multiple focused log files in one pass:

dotnet msbuild build.binlog -noconlog
-fl -flp:v=diag;logfile=full.log;performancesummary
-fl1 -flp1:errorsonly;logfile=errors.log
-fl2 -flp2:warningsonly;logfile=warnings.log

PowerShell note: Use -flp:"v=diag;logfile=full.log;performancesummary" (quoted semicolons).

Step 2: Read the errors

cat errors.log

This gives all errors with file paths, line numbers, error codes, and project context.

Step 3: Search for context around specific errors

Find all occurrences of a specific error code with surrounding context

grep -n -B2 -A2 "CS0246" full.log

Find which projects failed to compile

grep -i "CoreCompile.*FAILED|Build FAILED|error MSB" full.log

Find project build order and results

grep "done building project|Building with" full.log | head -50

Step 4: Detect cascading failures

Projects that never reached CoreCompile failed because a dependency failed, not their own code:

List all projects that ran CoreCompile

grep 'Target "CoreCompile"' full.log | grep -oP 'project "[^"]*"'

Compare against projects that had errors to identify cascading failures

grep "project.*FAILED" full.log

Step 5: Examine project files for root causes

Read the .csproj of the failing project

cat path/to/Services/Services.csproj

Check PackageReference and ProjectReference entries

grep -n "PackageReference|ProjectReference" path/to/Services/Services.csproj

Write your diagnosis as soon as you have enough information. Do not over-investigate.

Additional Workflows

Performance Investigation

The PerformanceSummary is at the end of full.log

tail -100 full.log # shows target/task timing summary grep "Target Performance Summary|Task Performance Summary" -A 50 full.log

Dependency/Evaluation Issues

Check evaluation properties

grep -i "OutputPath|IntermediateOutputPath|TargetFramework" full.log | head -30

Check item groups

grep "PackageReference|ProjectReference" full.log | head -30

Replay reference

Command Purpose

dotnet msbuild X.binlog -noconlog -fl -flp:v=diag;logfile=full.log;performancesummary

Full diagnostic log with perf summary

dotnet msbuild X.binlog -noconlog -fl -flp:errorsonly;logfile=errors.log

Errors only

dotnet msbuild X.binlog -noconlog -fl -flp:warningsonly;logfile=warnings.log

Warnings only

grep -n "PATTERN" full.log

Search for patterns in the replayed log

dotnet msbuild -pp:preprocessed.xml Proj.csproj

Preprocess — inline all imports into one file

Generating a binlog (only if none exists)

dotnet build /bl:build.binlog

Common error patterns

• CS0246 / "type not found" → Missing PackageReference — check the .csproj

• MSB4019 / "imported project not found" → SDK install or global.json issue

• NU1605 / "package downgrade" → Version conflict in package graph

• MSB3277 / "version conflicts" → Binding redirect or version alignment issue

• Project failed at ResolveProjectReferences → Cascading failure from a dependency