CodeDOM Tip: Generate a proper Using statement

I have done several projects over the year that require me to produce auto generate source code, mainly to avoid repetitive code tasks, to accomplish this I have used tools similar to CodeSmith. A couple of weeks ago I was tasked with auto-generating code using the CodeDOM, I was actually surprised to find out that this kind of source building framework existed natively, you can create every imaginable object type inherent to the .NET stack. Here is a simple example:

 
CodeCompileUnit compileUnit = new CodeCompileUnit();
CodeNamespace samples = new CodeNamespace("Samples");
samples.Imports.Add(new CodeNamespaceImport("System"));
CodeTypeDeclaration myclass = new CodeTypeDeclaration("Class1");
samples.Types.Add(myclass);

CSharpCodeProvider provider = new CSharpCodeProvider();
string sourceFile = nameof(myclass ) + provider.FileExtension;

using (StreamWriter sw = new StreamWriter(sourceFile, false))
{
    IndentedTextWriter tw = new IndentedTextWriter(sw, "    ");
    provider.GenerateCodeFromCompileUnit(compileUnit, tw,new CodeGeneratorOptions());
    tw.Close();
}

Now the above example is almost verbatim from MSDN, and actually outputs something like this, notice the misplaced using statement inside the names:

 
namespace Samples {
    using System;
    public class Class1 {}
}

To avoid this you need to initially create a blank namespace and add your required using statements there, later we add both namespaces to our CompileUnit like this:

 
CodeCompileUnit compileUnit = new CodeCompileUnit();
CodeNamespace blankNamespaces = new CodeNamespace();

blankNamespaces.Imports.Add(new CodeNamespaceImport("System"));
CodeNamespace samples = new CodeNamespace("Samples");
CodeTypeDeclaration myclass = new CodeTypeDeclaration("Class1");
samples.Types.Add(myclass);

compileUnit.Namespaces.Add(blankNamespaces);    // Add the blank using statement
compileUnit.Namespaces.Add(samples);

CSharpCodeProvider provider = new CSharpCodeProvider();
string sourceFile = nameof(myclass) + "." + provider.FileExtension;

using (StreamWriter sw = new StreamWriter(sourceFile, false))

IndentedTextWriter tw = new IndentedTextWriter(sw, "    ");
provider.GenerateCodeFromCompileUnit(compileUnit, tw, new CodeGeneratorOptions());
tw.Close();
}

This leads to a more syntactically appropriate source file

 
using System;
namespace Samples {
    public class Class1 {}
}