Saving Expression Tree to a File

Saving Expression Tree to a File

I want to debug an expression and save the expression tree to a file:
var generator = DebugInfoGenerator.CreatePdbGenerator();
var document = Expression.SymbolDocument(fileName: "MyDebug.txt");
var debugInfo = Expression.DebugInfo(document, 6, 9, 6, 22);
var expressionBlock = Expression.Block(debugInfo, fooExpression);
var lambda = Expression.Lambda(expressionBlock, parameters);
lambda.CompileToMethod(method, generator);
var bakedType = type.CreateType();
return (type)bakedType.GetMethod(method.Name).Invoke(null, parameters);
How can I find or save "MyDebug.txt"?