public static void AddAfterFirstItemGroup()
{
var project = Project.Load("testproj.csproj");
var itemGroup = new ItemGroup();
var newFile = new Compile("testfile.cs");
itemGroup.Add(newFile);
var firstItemGroup = project.ItemGroups.First();
firstItemGroup.AddAfterSelf(itemGroup);
var referenceItemGroup = new ItemGroup();
var guid = Guid.NewGuid();
var reference = new ProjectReference("../classlibrary/classlibrary.csproj")
{
Project = $"{{{guid}}}",
Name = "Some.Namespace",
};
// Add a Condition attribute to an item Metadata
reference.Metadata["Project"].Condition = " '${CustomProperty}' == 'CustomValue' ";
referenceItemGroup.Add(reference);
itemGroup.AddAfterSelf(referenceItemGroup);
project.Save();
}