Fix simplify lambda expression with unrelated assignment in other method

src/Analyzers/CSharp/Analyzers/RemoveUnnecessaryLambdaExpression/CSharpRemoveUnnecessaryLambdaExpressionDiagnosticAnalyzer.cs

@@ -183,8 +183,11 @@ private void AnalyzeSyntax(SyntaxNodeAnalysisContext context, INamedTypeSymbol?
             {
                 // Limit the search space to the outermost code block that could contain references to this expr (or
                 // fall back to compilation unit for top level statements).
-                var outermostBody = invokedExpression.AncestorsAndSelf().Last(
-                    n => n is BlockSyntax or ArrowExpressionClauseSyntax or AnonymousFunctionExpressionSyntax or CompilationUnitSyntax);
+                var outermostBody = invokedExpression.AncestorsAndSelf().LastOrDefault(
+                    n => n is BlockSyntax or ArrowExpressionClauseSyntax or AnonymousFunctionExpressionSyntax or GlobalStatementSyntax);
+                if (outermostBody is null or GlobalStatementSyntax)
+                    outermostBody = syntaxTree.GetRoot(cancellationToken);
+
                 foreach (var candidate in outermostBody.DescendantNodes().OfType<ExpressionSyntax>())
                 {
                     if (candidate != accessedExpression &&

src/Analyzers/CSharp/Tests/RemoveUnnecessaryLambdaExpression/RemoveUnnecessaryLambdaExpressionTests.cs

@@ -7,7 +7,6 @@
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.RemoveUnnecessaryLambdaExpression;
-using Microsoft.CodeAnalysis.CSharp.Shared.Extensions;
 using Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Roslyn.Test.Utilities;
@@ -1971,5 +1970,70 @@ internal Helper(Action<bool> action)
 
                 """);
         }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/71300")]
+        public async Task TestWithWriteInOtherMethod()
+        {
+            await TestInRegularAndScriptAsync("""
+                using System;
+                using System.Linq;
+
+                public class Repro
+                {
+                    private readonly MethodProvider _methodProvider;
+
+                    public Repro(MethodProvider methodProvider)
+                    {
+                        // Assignment that should not block feature.
+                        _methodProvider = methodProvider;
+                    }
+
+                    public void Main()
+                    {
+                        int[] numbers = { 1, 2, 3, 4, 5 };
+                        string[] asStrings = numbers.Select([|x => |]_methodProvider.ToStr(x)).ToArray();
+                        Console.WriteLine(asStrings.Length);
+                    }
+                }
+
+                public class MethodProvider
+                {
+                    public string ToStr(int x)
+                    {
+                        return x.ToString();
+                    }
+                }
+                """,
+                """
+                using System;
+                using System.Linq;
+
+                public class Repro
+                {
+                    private readonly MethodProvider _methodProvider;
+
+                    public Repro(MethodProvider methodProvider)
+                    {
+                        // Assignment that should not block feature.
+                        _methodProvider = methodProvider;
+                    }
+
+                    public void Main()
+                    {
+                        int[] numbers = { 1, 2, 3, 4, 5 };
+                        string[] asStrings = numbers.Select(_methodProvider.ToStr).ToArray();
+                        Console.WriteLine(asStrings.Length);
+                    }
+                }
+
+                public class MethodProvider
+                {
+                    public string ToStr(int x)
+                    {
+                        return x.ToString();
+                    }
+                }
+                """);
+        }
     }
 }