Codedom and String Processing

Question

I researched this, but couldn't find anything solid and wanted to see if anyone could point me in the right direction. I'm trying to see if Codedom can handle strings and consistency between different languages, without me setting conditional strings to the language.

For example, I need to generate the following, as shown below in both C # and VB.NET via Codedom:

FROM#

errorMsg = errorMsg.Replace('"', '\'').Replace("\r\n", @"\n"); System.Windows.Browser.HtmlPage.Window.Eval("throw new Error(\"Unhandled Error in Silverlight Application " + errorMsg + "\");"); 

Vb.net

 errorMsg = errorMsg.Replace(""""c, "'"c).Replace(ChrW(13) & ChrW(10), "\n") System.Windows.Browser.HtmlPage.Window.Eval("throw new Error(""Unhandled Error in Silverlight Application " + errorMsg + """);") 

CodeMethodInvokeExpression for errorMsg.Replace and System.Windows.Browser.HtmlPage.Window.Eval is simple enough, this is a line inside them that I cannot understand if Codedom can automatically handle.

Answer 1

Unfortunately, code primitives do not always produce the desired results when merging, because the provider will accept certain freedoms to interpret intentions. The way around this is to use CodeSnippetExpression .

Heres code (VB.NET and C #) that works to create the Eval statements that you provided in your question. Feel free to use what works best for you:

VB.NET Version

 Imports System.CodeDom Imports System.CodeDom.Compiler Imports System.Reflection Imports System.Text Imports System.IO Imports Microsoft.CSharp Public Class PrintEvalStatement Public provider As CodeDomProvider Sub New() Dim left As New CodePrimitiveExpression("throw new Error(""Unhandled Error in Silverlight Application ") Dim middle As New CodeVariableReferenceExpression("errorMsg") Dim right As New CodePrimitiveExpression(""");") Dim targetObject = New CodeTypeReferenceExpression("System.Windows.Browser.HtmlPage.Window") Dim methodName = "Eval" provider = New VBCodeProvider() Dim vbStatement As String = ConcatStatement(left, middle, right, targetObject, methodName) provider = New CSharpCodeProvider() Dim csStatement As String = ConcatStatement(left, middle, right, targetObject, methodName) Console.WriteLine(vbStatement) Console.WriteLine(csStatement) Console.ReadLine() End Sub Private Function ConcatStatement(ByVal left As CodePrimitiveExpression, ByVal middle As CodeVariableReferenceExpression, ByVal right As CodePrimitiveExpression, ByVal targetObject As CodeTypeReferenceExpression, ByVal methodName As String) As String Dim evalMessage As New CodeExpression evalMessage = ConcatString(left, middle, right) Dim eval As New CodeMethodInvokeExpression(targetObject, methodName, evalMessage) Dim evalStatement As New CodeExpressionStatement(eval) Dim sw As StringWriter = New StringWriter() Using tx As TextWriter = New StringWriter() provider.GenerateCodeFromStatement(evalStatement, tx, New CodeGeneratorOptions()) Return tx.ToString() End Using End Function Private Function ConcatString(ByVal left As CodeExpression, ByVal middle As CodeExpression, ByVal right As CodeExpression) As CodeExpression Return New CodeSnippetExpression(CodeToString(left) + " + " + CodeToString(middle) + " + " + CodeToString(right)) End Function Private Function CodeToString(ByVal expr As CodeExpression) As String Using tx As TextWriter = New StringWriter() provider.GenerateCodeFromExpression(expr, tx, New CodeGeneratorOptions()) Return tx.ToString() End Using End Function End Class 

C # Version

 using System.CodeDom; using System.CodeDom.Compiler; using System.Reflection; using System.Text; using System.IO; using Microsoft.CSharp; using Microsoft.VisualBasic; namespace CodeDom { class Program { static CodeDomProvider provider; static void Main(string[] args) { Program shell = new Program(); provider = new VBCodeProvider(); CodePrimitiveExpression left = new CodePrimitiveExpression("throw new Error(\"Unhandled Error in Silverlight Application\")"); CodeVariableReferenceExpression middle = new CodeVariableReferenceExpression("errorMsg"); CodePrimitiveExpression right = new CodePrimitiveExpression("\");"); CodeTypeReferenceExpression targetObject = new CodeTypeReferenceExpression("System.Windows.Browser.HtmlPage.Window"); string methodName = "Eval"; string vbStatement = shell.ConcatStatement(left, middle, right, targetObject, methodName); provider = new CSharpCodeProvider(); string csStatement = shell.ConcatStatement(left, middle, right, targetObject, methodName); Console.WriteLine(vbStatement); Console.WriteLine(csStatement); Console.ReadLine(); } public string ConcatStatement(CodePrimitiveExpression left, CodeVariableReferenceExpression middle, CodePrimitiveExpression right, CodeTypeReferenceExpression targetObject, string methodName) { CodeExpression evalMessage = new CodeExpression(); evalMessage = ConcatString(left, middle, right); CodeMethodInvokeExpression eval = new CodeMethodInvokeExpression(targetObject, methodName, evalMessage); CodeExpressionStatement evalStatement = new CodeExpressionStatement(eval); using (TextWriter tx = new StringWriter()) { provider.GenerateCodeFromStatement(evalStatement, tx, new CodeGeneratorOptions()); return tx.ToString(); } } private CodeExpression ConcatString(CodeExpression left, CodeExpression middle, CodeExpression right) { return new CodeSnippetExpression(CodeToString(left) + " + " + CodeToString(middle) + " + " + CodeToString(right)); } private string CodeToString(CodeExpression expr) { using (TextWriter tx = new StringWriter()) { provider.GenerateCodeFromExpression(expr,tx, new CodeGeneratorOptions()); return tx.ToString(); } } } } 

Answer 2

Update : I just tried the following code:

 VBCodeProvider vbProvider = new VBCodeProvider(); CSharpCodeProvider csProvider = new CSharpCodeProvider(); var errorMessagePart1 = new CodePrimitiveExpression("Unhandled Error in Silverlight Application \""); var errorMessagePart2 = new CodeVariableReferenceExpression("errorMsg"); var errorMessagePart3 = new CodePrimitiveExpression("\""); var errorMessage = new CodeBinaryOperatorExpression(new CodeBinaryOperatorExpression(errorMessagePart1, CodeBinaryOperatorType.Add, errorMessagePart2), CodeBinaryOperatorType.Add, errorMessagePart3); var expression = new CodeThrowExceptionStatement(new CodeObjectCreateExpression("Error", errorMessage)); StringWriter writer = new StringWriter(); vbProvider.GenerateCodeFromStatement(expression, writer, new CodeGeneratorOptions()); string vb = writer.ToString(); writer = new StringWriter(); csProvider.GenerateCodeFromStatement(expression, writer, new CodeGeneratorOptions()); string cs = writer.ToString(); Console.WriteLine(vb); Console.WriteLine(cs); 

He prints:

 Throw New [Error]((("Unhandled Error in Silverlight Application """ + errorMsg) _ + """")) throw new Error((("Unhandled Error in Silverlight Application \"" + errorMsg) + "\"")); 

Which looks to me like a VB version and a C # version. Not everything you can do about false parentheses, but should not do any harm.

Answer 3

You can call string.Concat instead of using the + operator if you do not need to generate the code exactly as shown.

 CodePrimitiveExpression throwstring = new CodePrimitiveExpression("throw new Error(\"Unhandled Error in Silverlight Application "); CodeVariableReferenceExpression errorMsg = new CodeVariableReferenceExpression("errorMsg"); CodePrimitiveExpression end = new CodePrimitiveExpression("\");"); CodeTypeReferenceExpression targetObject = new CodeTypeReferenceExpression("System.Windows.Browser.HtmlPage.Window"); CodeTypeReferenceExpression str = new CodeTypeReferenceExpression(typeof(string)); CodeMethodInvokeExpression concat = new CodeMethodInvokeExpression(str,"Concat",throwstring,errorMsg,end); CodeMethodInvokeExpression invoke = new CodeMethodInvokeExpression(new CodeMethodReferenceExpression(targetObject, "Eval"), concat); 

C # Outputs:

 System.Windows.Browser.HtmlPage.Window.Eval(string.Concat("throw new Error(\"Unhandled Error in Silverlight Application ", errorMsg, "\");")) 

VB:

 System.Windows.Browser.HtmlPage.Window.Eval(String.Concat("throw new Error(""Unhandled Error in Silverlight Application ", errorMsg, """);")) 

Answer 4

The CodeTypeReference class should help you ( http://msdn.microsoft.com/en-us/library/system.codedom.codetypereference.aspx ), as Alison did.