这里我们需要特别注意的是 XamlReader 载入的 XAML 代码不能包含任何类型(x:Class)以及事件代码(x:Code)，也就是说要XAML自身的代码才受支持(这个也在WPF揭秘这本书讲到过)。那么我们可以用 XamlWriter 将一个编译的 BAML 还原成 XAML了，具体代码如下：
//XamlWritervar
xaml = XamlWriter.Save(new
Window2());
MessageBox.Show(xaml);
xaml = XamlWriter.Save(new
Window2());
MessageBox.Show(xaml);
输出的Message如下(为了效果更好看一些，我粘贴到了VS):
<Window2 Title="Window2" idth="300"Height="300"
xmlns="clr-namespace:XamlReaderWriterDemo;
assembly=XamlReaderWriterDemo"
xmlns:av="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<av:Grid>
<av:Button Name="btnTest" Height="23" Margin="98,72,105,0" VerticalAlignment="Top">
Button
</av:Button>
</av:Grid>
</Window2>
xmlns="clr-namespace:XamlReaderWriterDemo;
assembly=XamlReaderWriterDemo"
xmlns:av="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<av:Grid>
<av:Button Name="btnTest" Height="23" Margin="98,72,105,0" VerticalAlignment="Top">
Button
</av:Button>
</av:Grid>
</Window2>
XAML 的动态载入在使用动态换肤以及运行时加载等场景颇为有用，以后也会慢慢接触。
由于使用XamlReader和XamlWriter有很多限制，比如我想把一批Baml转化为Xaml，再比如我想指定Baml的路径，然后通过Load的方式载入，那么这些场景就无法通过XamlReader和XamlWriter完成了，这个让我也做过不少的Demo，也跟踪了很长时间的IL代码，在百思不得其解之后和周永恒、Virus等讨论了一下，最后终于找到了一个方案，如下代码所示：
public static class BamlWriter {
public static void Save(object obj, Stream stream)
{
string path = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
Directory.CreateDirectory(path);
try
{
string xamlFile = Path.Combine(path, "input.xaml");
string projFile = Path.Combine(path, "project.proj");
using (FileStream fs = File.Create(xamlFile))
{
XamlWriter.Save(obj, fs);
}
Engine engine = new Engine();
engine.BinPath = RuntimeEnvironment.GetRuntimeDirectory();
Project project = engine.CreateNewProject();
BuildPropertyGroup pgroup = project.AddNewPropertyGroup(false);
pgroup.AddNewProperty("AssemblyName", "temp");
pgroup.AddNewProperty("OutputType", "Library");
pgroup.AddNewProperty("IntermediateOutputPath", ".");
pgroup.AddNewProperty("MarkupCompilePass1DependsOn", "ResolveReferences");
BuildItemGroup igroup = project.AddNewItemGroup();
igroup.AddNewItem("Page", "input.xaml");
igroup.AddNewItem("Reference", "WindowsBase");
igroup.AddNewItem("Reference", "PresentationCore");
igroup.AddNewItem("Reference", "PresentationFramework");
project.AddNewImport(@"$(MSBuildBinPath)\Microsoft.CSharp.targets", null);
project.AddNewImport(@"$(MSBuildBinPath)\Microsoft.WinFX.targets", null);
project.FullFileName = projFile;
if (engine.BuildProject(project, "MarkupCompilePass1"))
{
byte[] buffer = new byte[1024];
using (FileStream fs = File.OpenRead(Path.Combine(path, "input.baml")))
{
int read = 0;
while (0 < (read = fs.Read(buffer, 0, buffer.Length)))
{
stream.Write(buffer, 0, read);
}
}
}
else
{
throw new System.Exception("Baml compilation failed.");
}
}
finally
{
Directory.Delete(path, true);
}
}
}
public static class BamlReader
{
public static object Load(Stream stream)
{
ParserContext pc = new ParserContext();
return typeof(XamlReader)
.GetMethod("LoadBaml", BindingFlags.NonPublic | BindingFlags.Static)
.Invoke(null, new object[] { stream, pc, null, false });
}
}
public static void Save(object obj, Stream stream)
{
string path = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
Directory.CreateDirectory(path);
try
{
string xamlFile = Path.Combine(path, "input.xaml");
string projFile = Path.Combine(path, "project.proj");
using (FileStream fs = File.Create(xamlFile))
{
XamlWriter.Save(obj, fs);
}
Engine engine = new Engine();
engine.BinPath = RuntimeEnvironment.GetRuntimeDirectory();
Project project = engine.CreateNewProject();
BuildPropertyGroup pgroup = project.AddNewPropertyGroup(false);
pgroup.AddNewProperty("AssemblyName", "temp");
pgroup.AddNewProperty("OutputType", "Library");
pgroup.AddNewProperty("IntermediateOutputPath", ".");
pgroup.AddNewProperty("MarkupCompilePass1DependsOn", "ResolveReferences");
BuildItemGroup igroup = project.AddNewItemGroup();
igroup.AddNewItem("Page", "input.xaml");
igroup.AddNewItem("Reference", "WindowsBase");
igroup.AddNewItem("Reference", "PresentationCore");
igroup.AddNewItem("Reference", "PresentationFramework");
project.AddNewImport(@"$(MSBuildBinPath)\Microsoft.CSharp.targets", null);
project.AddNewImport(@"$(MSBuildBinPath)\Microsoft.WinFX.targets", null);
project.FullFileName = projFile;
if (engine.BuildProject(project, "MarkupCompilePass1"))
{
byte[] buffer = new byte[1024];
using (FileStream fs = File.OpenRead(Path.Combine(path, "input.baml")))
{
int read = 0;
while (0 < (read = fs.Read(buffer, 0, buffer.Length)))
{
stream.Write(buffer, 0, read);
}
}
}
else
{
throw new System.Exception("Baml compilation failed.");
}
}
finally
{
Directory.Delete(path, true);
}
}
}
public static class BamlReader
{
public static object Load(Stream stream)
{
ParserContext pc = new ParserContext();
return typeof(XamlReader)
.GetMethod("LoadBaml", BindingFlags.NonPublic | BindingFlags.Static)
.Invoke(null, new object[] { stream, pc, null, false });
}
}
上面的代码，大家可以试一下运行效果。或者有更好的方式也请告知。
七，本文总结
本篇主要对前几次的课程进了一些简单的回顾，同时用一个比较全的Demo介绍了Xaml中引用各种控件和类等，另外对脱离VS工具CSC编译WPF以及XamlReader与XamlWriter 做了比较详细的介绍。下篇我们将进入WPF布局的世界进行漫游，争取和布局控件及应用来一个全接触!
最后圣殿骑士 会尽心尽力写好这个系列，同时由于是自己对这些技术的使用总结和心得体会，错误之处在所难免，怀着技术交流的心态，在博客园和51CTO发表出来，所以希望大家能够多多指点，这样在使一部分人受益的同时也能纠正我的错误观点，以便和各位共同提高，后续文章敬请关注!
