Compare assemblies
dotPeek allows you to compare two assemblies or two different versions of the same assembly. Each comparison is presented as a separate top-level node in the Assembly Explorer; you can expand this node and see differences in the assembly structure right away, and in addition to that, you can double-click types, members and other elements to see a text-based comparison in the code viewer.
Initiate comparison
Click Compare Two Assemblies on the Assembly Explorer toolbar or choose from the menu , select two assembly files for comparison in the dialog that opens, and click OK.
Alternatively, right-click an assembly in the Assembly Explorer, choose Compare With, and then select an assembly file for comparison.
The comparison will appear as a new top-level node in the Assembly Explorer.
Elements within the comparison node (types, members, files) are highlighted in different colors with the following meanings:
Green — the element is present in the second assembly and absent in the first assembly.
Red — the element is present in the first assembly and absent in the second assembly.
Violet — the element is present in both assemblies, and it has differences.
When you double-click an element with differences, the comparison opens in an external diff tool. If the diff tool is not specified, a dialog will appear where you can specify it: 
If you have Visual Studio or KDiff installed on your machine, you can click the corresponding button to use one of these tools. Alternatively, specify the path to a diff tool and command line arguments to open the compared documents. The documents are referred to as $1 and $2. The selected tool and its arguments will be saved for later comparisons, and you can change it on the page of dotPeek options Ctrl+Alt+S.
To finish comparing assemblies, select the comparison node and press Delete or right-click it and choose Remove Item from List.