Figure 6-9: Main ILDASM display in Visual C#

Printing Code 3 of 9 in Visual C# Figure 6-9: Main ILDASM display

Table 6-2: ILDASM Tree Output Descriptions Glyph Text Output [MOD] for heading [NSP] [CLS] [INT] [ENU] [VCL] [MET] module Description Informational directives, class declarations, and manifest information Namespace Class Interface Enumeration Value class Instance method (private, public, or protected) 222

Table 6-2: ILDASM Tree Output Descriptions Glyph Text Output [STM] [FLD] [STF] [EVT] [PTY] Description Static method Instance field (private, protected); also assembly Static field Event Property (get and/or set) public, or

If you'd like to see more information and statistics about files you're opening, start ILDASM with the /ADV command line option. This turns on advanced display information and appends three new items to the View menu: COR Header lets you view the file header information. Statistics lets you see various statistics concerning size percentages and a breakdown of all metadata in the system. MetaInfo contains a submenu that lets you select specific information to view. Choose the Show! submenu item (or press Ctrl+M) to see that information, which is displayed in a separate MetaInfo window. If you don't select any of the specific information, when you select Show!, you'll see a raw dump of the metadata. If you have source code available for a particular module, you'll certainly want to turn on Show Source Lines on the View menu. Alternatively, you can specify the /SOURCE command line option. When you specify source line display, the disassembly shows the source lines as comments above the MSIL generated for them. To see all the commandline options, specify / on the command line. I use a batch file that contains the following to start instances of ILDASM with the options I want: ildasm /adv /source %1 To see the actual MSIL for a particular item, simply double-click on that item and another window will pop up. Depending on what you double-clicked, you'll see the disassembly, declaration information, or general information for the item. If the window looks like the one in Figure 6-10, you're ready to start learning MSIL. One nice little feature of ILDASM is that it supports drag-and-drop functionality, so you can easily jump between modules.

Figure 6-10: MSIL for a method The final trick I want to share about ILDASM is how you can see your C#, J#, Managed Extensions for C++, or Visual Basic .NET code and the MSIL all at the same time. If you've looked at the debugger's Disassembly window when debugging a managed application, you've probably seen the .NET language code and only the Intel assembly language. The reason is that the MSIL is just-in-time (JIT) compiled, so you're only executing the native assembly language, never the MSIL. What makes ILDASM really interesting is that it achieves the Holy Grail of disassemblers: it's a true "round-trip" disassembler! With a round-trip disassembler, you can disassemble a binary and immediately run it through an assembler to rebuild the application. Since .NET comes with ILASM, the Microsoft Intermediate Language Assembler, you've got everything you need to see your C#/J#/Managed Extensions for C++/Visual Basic .NET code and MSIL all at the same time. This view allows you to see how things fit together. Disassemble the file with the /SOURCE and /OUT= command-line options to ILDASM, specifying an output file name that ends in .IL. Compile the file with ILASM using the /DEBUG option. Now you'll step through the MSIL with Visual Studio .NET's debugger and see the corresponding C#/J#/Managed Extensions for C++/Visual Basic .NET code as comments. If you want to see it all, simply look at the Disassembly window and you'll see how the high-level language is compiled to MSIL, and how the MSIL is JIT compiled to Intel assembly language. Listing 6-2 shows a method disassembled with the original source embedded as comments from the ShowBPs program, included with this book's sample files. Listing 6-2: Mixed source and MSIL

.method private instance void btnConditionalBreaks_Click(object sender, class [mscorlib]System.EventArgs e) cil managed { // Code size .maxstack 4 139 (0x8b)

.locals init ([0] int32 i, [1] int32 j, [2] string[] _Vb_t_array_0, [3] class [System.Windows.Forms] System.Windows.Forms.TextBox _Vb_t_ref_0) //000120: //000121: Private Sub btnConditionalBreaks_Click _ // // // IL_0000: //000122: IL_0001: IL_0002: //000123: IL_0003: IL_0004: //000124: //000125: ' Clearn the output edit control. //000126: edtOutput.Clear() IL_0005: IL_0006: ldarg.0 callvirt instance class [System.Windows.Forms]System.Windows.Forms.TextBox ShowBPs.ShowBPsForm::get_edtOutput() IL_000b: callvirt instance void nop Dim i As Integer = 0 ldc.i4.0 stloc.0 Dim j As Integer = 0 ldc.i4.0 stloc.1 ( ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnConditionalBreaks.Click

[System.Windows.Forms]System.Windows.Forms.TextBoxBase::Clear() IL_0010: //000127: //000128: ' Both are on one line to show how BPs can apply to part of a line. //000129: For i = 1 To 5 : For j = 1 To 5 IL_0011: ldc.i4.1 225 nop

IL_0012: IL_0013: IL_0014: