问题
I have a string string input;
with some code (all below is in that string)
var x = s.IndexOf("a");
return String.Format(s, x);
Now, I would like to achieve following scenario:
Func<string, string> f = Compile(input);
var test = "dcba - {0}";
var result = f(test);
// result = "dcba - 3";
I assume, that the actual T1, TResult are known (here: string, string), and that input is named "s". I can achieve it this way:
var input = "var x = s.IndexOf(\"a\"); return String.Format(s, x);";
var containerClass = @"using System; class TempClass {{ public string temp_func(string s){{ {0} }} }}";
var code = String.Format(containerClass, input);
// Create a new instance of the C# compiler
var compiler = new CSharpCodeProvider();
var params = new CompilerParameters
{
GenerateExecutable = false,
GenerateInMemory = true
};
params.ReferencedAssemblies.Add("System.dll");
var results = compiler.CompileAssemblyFromSource(params, code);
Func<string, string> f;
if (results.Errors.Count == 0)
{
f = s =>
{
var myClass = results.CompiledAssembly.CreateInstance("TempClass");
return (string) myClass.GetType().
GetMethod("temp_func").
Invoke(myClass, new object[] {s});
};
// test:
Console.WriteLine(f(Console.ReadLine()));
}
But it is fairly complicated way. Is there any way to simplify this, if I know that I just want a Func<T1, TResult>
, not a whole compiled assembly, instancing classes (or calling a static method on one)?
I can take this code, of course, and dress it nicely - wrap it in a generic class, get T1, TResult type names to put into the TempClass
template (String.Format("public {0} temp_func({1} s)",typeof(TResult).Name, typeof(T1).Name);
), but it has a feel of greasing an axle of a square wheel to make ride smoother...
回答1:
I went with something like this:
public class DynamicFunction
{
private static int _counter = 0;
private const string ClassBody = "{2} public static class DynamicFunctionHost{0} {{ {1} }}";
private const string ClassName = "DynamicFunctionHost{0}";
private const string FunctionName = "func";
private const string T1FuncBody = "public static {1} func({0} param1){{ {2} }}";
public static Func<T1, TResult> Get<T1, TResult>(string funcBody, string[] referenced, string[] usingNs)
{
var code = String.Format(ClassBody, _counter,
String.Format(T1FuncBody, typeof (T1).Name, typeof (TResult).Name, funcBody),
String.Join("\n", usingNs.Select(r => String.Format("using {0};", r))));
var result = Compile(code, referenced);
var host =
result.CompiledAssembly.DefinedTypes.Single(
typeinfo => typeinfo.FullName.Equals(String.Format(ClassName, _counter)));
++_counter;
return input => (TResult) host.GetMethod(FunctionName).Invoke(null, new object[] { input });
}
private static CompilerResults Compile(string code, string[] referenced)
{
var compiler = new CSharpCodeProvider();
var parameters = new CompilerParameters
{
GenerateExecutable = false,
GenerateInMemory = true
};
foreach (var r in referenced)
parameters.ReferencedAssemblies.Add(r);
var results = compiler.CompileAssemblyFromSource(parameters, code);
if (results.Errors.Count == 0) return results;
// else
var e = new ArgumentException("Errors during compilation", "code");
e.Data.Add("Errors", results.Errors);
throw e;
}
}
The use is fairly simple then:
var f = DynamicFunction.Get<string, string[]>("return param1.ToCharArray()", new []{"System.dll","System.Core.dll"}, new []{"System"});
var x = f("abcd"); // =[a,b,c,d]
来源:https://stackoverflow.com/questions/28226271/compile-funct1-tresult-from-string-on-the-fly