Decompile a method exception error

Decompile a method exception error and extracted source not compile.
Thanks so much.
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http://www.solidfiles.com/d/537442f0de/

ICSharpCode.Decompiler.DecompilerException: Error decompiling ns0.Class41 ns0.Class41::method_36(System.Int32)
---> System.NullReferenceException: Object reference not set to an instance of an object.
at ICSharpCode.Decompiler.ILAst.TypeAnalysis.DoInferTypeForExpression(ILExpression expr, TypeReference expectedType, Boolean forceInferChildren)
at ICSharpCode.Decompiler.ILAst.TypeAnalysis.InferTypeForExpression(ILExpression expr, TypeReference expectedType, Boolean forceInferChildren)
at ICSharpCode.Decompiler.ILAst.TypeAnalysis.RunInference(ILExpression expr)
at ICSharpCode.Decompiler.ILAst.TypeAnalysis.RunInference(ILExpression expr)
at ICSharpCode.Decompiler.ILAst.TypeAnalysis.RunInference()
at ICSharpCode.Decompiler.ILAst.ILAstOptimizer.Optimize(DecompilerContext context, ILBlock method, ILAstOptimizationStep abortBeforeStep)
at ICSharpCode.Decompiler.Ast.AstMethodBodyBuilder.CreateMethodBody(IEnumerable1 parameters)
at ICSharpCode.Decompiler.Ast.AstMethodBodyBuilder.CreateMethodBody(MethodDefinition methodDef, DecompilerContext context, IEnumerable1 parameters)
--- End of inner exception stack trace ---
at ICSharpCode.Decompiler.Ast.AstMethodBodyBuilder.CreateMethodBody(MethodDefinition methodDef, DecompilerContext context, IEnumerable`1 parameters)
at ICSharpCode.Decompiler.Ast.AstBuilder.CreateMethod(MethodDefinition methodDef)
at ICSharpCode.Decompiler.Ast.AstBuilder.AddMethod(MethodDefinition method)
at ICSharpCode.ILSpy.CSharpLanguage.DecompileMethod(MethodDefinition method, ITextOutput output, DecompilationOptions options)
at ICSharpCode.ILSpy.TextView.DecompilerTextView.DecompileNodes(DecompilationContext context, ITextOutput textOutput)
at ICSharpCode.ILSpy.TextView.DecompilerTextView.<>c__DisplayClass17.b__16()