Advanced C# compiler options

The following options support advanced scenarios. The new MSBuild syntax is shown in Bold. The older csc.exe syntax is shown in code style.

  • MainEntryPoint, StartupObject / -main: Specify the type that contains the entry point.
  • PdbFile / -pdb: Specify debug information file name.
  • PathMap / -pathmap: Specify a mapping for source path names output by the compiler.
  • ApplicationConfiguration / -appconfig: Specify an application configuration file containing assembly binding settings.
  • AdditionalLibPaths / -lib: Specify additional directories to search in for references.
  • GenerateFullPaths / -fullpath: Compiler generates fully qualified paths.
  • PreferredUILang / -preferreduilang: Specify the preferred output language name.
  • BaseAddress / -baseaddress: Specify the base address for the library to be built.
  • ChecksumAlgorithm / -checksumalgorithm : Specify algorithm for calculating source file checksum stored in PDB.
  • CodePage / -codepage: Specify the codepage to use when opening source files.
  • Utf8Output / -utf8output: Output compiler messages in UTF-8 encoding.
  • FileAlignment / -filealign: Specify the alignment used for output file sections.
  • ErrorEndLocation / -errorendlocation: Output line and column of the end location of each error.
  • NoStandardLib / -nostdlib: Don't reference standard library mscorlib.dll.
  • SubsystemVersion / -subsystemversion: Specify subsystem version of this assembly.
  • ModuleAssemblyName / -moduleassemblyname: Name of the assembly that this module will be a part of.
  • ReportIVTs / -reportivts: Produce additional information on System.Runtime.CompilerServices.InternalsVisibleToAttribute information.

You add any of these options in a <PropertyGroup> element in your *.csproj file:


MainEntryPoint or StartupObject

This option specifies the class that contains the entry point to the program, if more than one class contains a Main method.




Where Program is the type that contains the Main method. The provided class name must be fully qualified; it must include the full namespace containing the class, followed by the class name. For example, when the Main method is located inside the Program class in the MyApplication.Core namespace, the compiler option has to be -main:MyApplication.Core.Program. If your compilation includes more than one type with a Main method, you can specify which type contains the Main method.


This option can't be used for a project that includes top-level statements, even if that project contains one or more Main methods.


The PdbFile compiler option specifies the name and location of the debug symbols file. The filename value specifies the name and location of the debug symbols file.


When you specify DebugType, the compiler creates a .pdb file in the same directory where the compiler creates the output file (.exe or .dll). The .pdb file has the same base file name as the name of the output file. PdbFile allows you to specify a nondefault file name and location for the .pdb file. This compiler option can't be set in the Visual Studio development environment, nor can it be changed programmatically.



Specifying PathMap will prevent breakpoints from working in local debug builds. Only set PathMap for production or continuous integration builds.

The PathMap compiler option specifies how to map physical paths to source path names output by the compiler. This option maps each physical path on the machine where the compiler runs to a corresponding path that should be written in the output files. In the following example, path1 is the full path to the source files in the current environment, and sourcePath1 is the source path substituted for path1 in any output files. To specify multiple mapped source paths, separate each with a comma.


The compiler writes the source path into its output for the following reasons:

  1. The source path is substituted for an argument when the CallerFilePathAttribute is applied to an optional parameter.
  2. The source path is embedded in a PDB file.
  3. The path of the PDB file is embedded into a PE (portable executable) file.


The ApplicationConfiguration compiler option enables a C# application to specify the location of an assembly's application configuration (app.config) file to the common language runtime (CLR) at assembly binding time.


Where file is the application configuration file that contains assembly binding settings. One use of ApplicationConfiguration is advanced scenarios in which an assembly has to reference both the .NET Framework version and the .NET Framework for Silverlight version of a particular reference assembly at the same time. For example, a XAML designer written in Windows Presentation Foundation (WPF) might have to reference both the WPF Desktop, for the designer's user interface, and the subset of WPF that is included with Silverlight. The same designer assembly has to access both assemblies. By default, the separate references cause a compiler error, because assembly binding sees the two assemblies as equivalent. The ApplicationConfiguration compiler option enables you to specify the location of an app.config file that disables the default behavior by using a <supportPortability> tag, as shown in the following example.

<supportPortability PKT="7cec85d7bea7798e" enable="false"/>

The compiler passes the location of the file to the CLR's assembly-binding logic.


To use the app.config file that is already set in the project, add property tag <UseAppConfigForCompiler> to the .csproj file and set its value to true. To specify a different app.config file, add property tag <AppConfigForCompiler> and set its value to the location of the file.

The following example shows an app.config file that enables an application to have references to both the .NET Framework implementation and the .NET Framework for Silverlight implementation of any .NET Framework assembly that exists in both implementations. The ApplicationConfiguration compiler option specifies the location of this app.config file.

      <supportPortability PKT="7cec85d7bea7798e" enable="false"/>
      <supportPortability PKT="31bf3856ad364e35" enable="false"/>


The AdditionalLibPaths option specifies the location of assemblies referenced with the References option.


Where dir1 is a directory for the compiler to look in if a referenced assembly isn't found in the current working directory (the directory from which you're invoking the compiler) or in the common language runtime's system directory. dir2 is one or more additional directories to search in for assembly references. Separate directory names with a comma, and without white space between them. The compiler searches for assembly references that aren't fully qualified in the following order:

  1. Current working directory.
  2. The common language runtime system directory.
  3. Directories specified by AdditionalLibPaths.
  4. Directories specified by the LIB environment variable.

Use Reference to specify an assembly reference. AdditionalLibPaths is additive. Specifying it more than once appends to any prior values. Since the path to the dependent assembly isn't specified in the assembly manifest, the application will find and use the assembly in the global assembly cache. The compiler referencing the assembly doesn't imply the common language runtime can find and load the assembly at run time. See How the Runtime Locates Assemblies for details on how the runtime searches for referenced assemblies.


The GenerateFullPaths option causes the compiler to specify the full path to the file when listing compilation errors and warnings.


By default, errors and warnings that result from compilation specify the name of the file in which an error was found. The GenerateFullPaths option causes the compiler to specify the full path to the file. This compiler option is unavailable in Visual Studio and can't be changed programmatically.


By using the PreferredUILang compiler option, you can specify the language in which the C# compiler displays output, such as error messages.


Where language is the language name of the language to use for compiler output. You can use the PreferredUILang compiler option to specify the language that you want the C# compiler to use for error messages and other command-line output. If the language pack for the language isn't installed, the language setting of the operating system is used instead.


The BaseAddress option lets you specify the preferred base address at which to load a DLL. For more information about when and why to use this option, see Larry Osterman's WebLog.


Where address is the base address for the DLL. This address can be specified as a decimal, hexadecimal, or octal number. The default base address for a DLL is set by the .NET common language runtime. The lower-order word in this address will be rounded. For example, if you specify 0x11110001, it is rounded to 0x11110000. To complete the signing process for a DLL, use SN.EXE with the -R option.


This option controls the checksum algorithm we use to encode source files in the PDB.


The algorithm must be either SHA1 (default) or SHA256.


This option specifies which codepage to use during compilation if the required page isn't the current default codepage for the system.


Where id is the ID of the code page to use for all source code files in the compilation. The compiler first attempts to interpret all source files as UTF-8. If your source code files are in an encoding other than UTF-8 and use characters other than 7-bit ASCII characters, use the CodePage option to specify which code page should be used. CodePage applies to all source code files in your compilation. See GetCPInfo for information on how to find which code pages are supported on your system.


The Utf8Output option displays compiler output using UTF-8 encoding.


In some international configurations, compiler output can't correctly be displayed in the console. Use Utf8Output and redirect compiler output to a file.


The FileAlignment option lets you specify the size of sections in your output file. Valid values are 512, 1024, 2048, 4096, and 8192. These values are in bytes.


You set the FileAlignment option from the Advanced page of the Build properties for your project in Visual Studio. Each section is aligned on a boundary that is a multiple of the FileAlignment value. There's no fixed default. If FileAlignment isn't specified, the common language runtime picks a default at compile time. By specifying the section size, you affect the size of the output file. Modifying section size may be useful for programs that run on smaller devices. Use DUMPBIN to see information about sections in your output file.


Instructs the compiler to output line and column of the end location of each error.


By default, the compiler writes the starting location in source for all errors and warnings. When this option is set to true, the compiler writes both the starting and end location for each error and warning.


NoStandardLib prevents the import of mscorlib.dll, which defines the entire System namespace.


Use this option if you want to define or create your own System namespace and objects. If you don't specify NoStandardLib, mscorlib.dll is imported into your program (same as specifying <NoStandardLib>false</NoStandardLib>).


Specifies the minimum version of the subsystem on which the executable file runs. Most commonly, this option ensures that the executable file can use security features that aren’t available with older versions of Windows.


To specify the subsystem itself, use the TargetType compiler option.


The major.minor specify the minimum required version of the subsystem, as expressed in a dot notation for major and minor versions. For example, you can specify that an application can't run on an operating system that's older than Windows 7. Set the value of this option to 6.01, as the table later in this article describes. You specify the values for major and minor as integers. Leading zeroes in the minor version don't change the version, but trailing zeroes do. For example, 6.1 and 6.01 refer to the same version, but 6.10 refers to a different version. We recommend expressing the minor version as two digits to avoid confusion.

The following table lists common subsystem versions of Windows.

Windows version Subsystem version
Windows Server 2003 5.02
Windows Vista 6.00
Windows 7 6.01
Windows Server 2008 6.01
Windows 8 6.02

The default value of the SubsystemVersion compiler option depends on the conditions in the following list:

  • The default value is 6.02 if any compiler option in the following list is set:
  • The default value is 6.00 if you're using MSBuild, you're targeting .NET Framework 4.5, and you haven't set any of the compiler options that were specified earlier in this list.
  • The default value is 4.00 if none of the previous conditions are true.


Specifies the name of an assembly whose nonpublic types a .netmodule can access.


ModuleAssemblyName should be used when building a .netmodule, and where the following conditions are true:

  • The .netmodule needs access to nonpublic types in an existing assembly.
  • You know the name of the assembly into which the .netmodule will be built.
  • The existing assembly has granted friend assembly access to the assembly into which the .netmodule will be built.

For more information on building a .netmodule, see TargetType option of module. For more information on friend assemblies, see Friend Assemblies.


Enable or disable additional diagnostic information about System.Runtime.CompilerServices.InternalsVisibleToAttribute found during the compilation:


The diagnostics are enabled if the element content is true, disabled if false, or not present.

ReportIVTs reports the following information when enabled:

  1. Any inaccessible member diagnostics include their source assembly, if different than the current assembly.
  2. The compiler prints the assembly identity of the project being compiled, its assembly name and public key.
  3. For every reference passed to the compiler, it prints;
    1. The assembly identity of the reference
    2. Whether the reference grants the current project InternalsVisibleTo
    3. The name and all public keys of any assemblies granted InternalsVisibleTo from this assembly