BadImageFormatException Class

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Source:

BadImageFormatException.cs

The exception that is thrown when the file image of a dynamic link library (DLL) or an executable program is invalid.

public ref class BadImageFormatException : SystemException

public class BadImageFormatException : SystemException

type BadImageFormatException = class
    inherit SystemException

Public Class BadImageFormatException
Inherits SystemException

Inheritance

Object

Exception

SystemException

BadImageFormatException

Remarks

This exception is thrown when the file format of a dynamic link library (.dll file) or an executable (.exe file) doesn't conform to the format that the common language runtime expects. In particular, the exception is thrown under the following conditions:

• An earlier version of a .NET utility, such as ILDasm.exe or installutil.exe, is used with an assembly that was developed with a later version of .NET.

  To address this exception, use the version of the tool that corresponds to the version of .NET that was used to develop the assembly. This may require modifying the Path environment variable or providing a fully qualified path to the correct executable.

• You are trying to load an unmanaged dynamic link library or executable (such as a Windows system DLL) as if it were a .NET assembly. The following example illustrates this by using the Assembly.LoadFile method to load Kernel32.dll.

  // Windows DLL (non-.NET assembly)
  string filePath = Environment.ExpandEnvironmentVariables("%windir%");
  if (! filePath.Trim().EndsWith(@"\"))
     filePath += @"\";
  filePath += @"System32\Kernel32.dll";
  
  try {
     Assembly assem = Assembly.LoadFile(filePath);
  }
  catch (BadImageFormatException e) {
     Console.WriteLine("Unable to load {0}.", filePath);
     Console.WriteLine(e.Message.Substring(0,
                       e.Message.IndexOf(".") + 1));
  }
  // The example displays an error message like the following:
  //       Unable to load C:\WINDOWS\System32\Kernel32.dll.
  //       The module was expected to contain an assembly manifest.
  

  open System
  open System.Reflection
  
  // Windows DLL (non-.NET assembly)
  let filePath = 
      let filePath = Environment.ExpandEnvironmentVariables "%windir%"
      let filePath =
          if not (filePath.Trim().EndsWith @"\") then
              filePath + @"\"
          else filePath
      filePath + @"System32\Kernel32.dll"
  
  try
      Assembly.LoadFile filePath |> ignore
  with :? BadImageFormatException as e ->
     printfn $"Unable to load {filePath}."
     printfn $"{e.Message[0 .. e.Message.IndexOf '.']}"
  
  // The example displays an error message like the following:
  //       Unable to load C:\WINDOWS\System32\Kernel32.dll.
  //       Bad IL format.
  

  ' Windows DLL (non-.NET assembly)
  Dim filePath As String = Environment.ExpandEnvironmentVariables("%windir%")
  If Not filePath.Trim().EndsWith("\") Then filepath += "\"
  filePath += "System32\Kernel32.dll"
  Try
     Dim assem As Assembly = Assembly.LoadFile(filePath)
  Catch e As BadImageFormatException
     Console.WriteLine("Unable to load {0}.", filePath)
     Console.WriteLine(e.Message.Substring(0, _
                       e.Message.IndexOf(".") + 1))   
  End Try
  ' The example displays an error message like the following:
  '       Unable to load C:\WINDOWS\System32\Kernel32.dll.
  '       The module was expected to contain an assembly manifest.
  

  To address this exception, access the methods defined in the DLL by using the features provided by your development language, such as the Declare statement in Visual Basic or the DllImportAttribute attribute with the extern keyword in C# and F#.

• You are trying to load a reference assembly in a context other than the reflection-only context. You can address this issue in either of two ways:

  • You can load the implementation assembly rather than the reference assembly.
  • You can load the reference assembly in the reflection-only context by calling the Assembly.ReflectionOnlyLoad method.

• A DLL or executable is loaded as a 64-bit assembly, but it contains 32-bit features or resources. For example, it relies on COM interop or calls methods in a 32-bit dynamic link library.

  To address this exception, set the project's Platform target property to x86 (instead of x64 or AnyCPU) and recompile.

• Your application's components were created using different versions of .NET. Typically, this exception occurs when an application or component that was developed using the .NET Framework 1.0 or the .NET Framework 1.1 tries to load an assembly that was developed using the .NET Framework 2.0 SP1 or later, or when an application that was developed using the .NET Framework 2.0 SP1 or .NET Framework 3.5 tries to load an assembly that was developed using the .NET Framework 4 or later. The BadImageFormatException may be reported as a compile-time error, or the exception may be thrown at run time. The following example defines a StringLib class that has a single member, ToProperCase, and that resides in an assembly named StringLib.dll.

  using System;
  
  public class StringLib
  {
     private string[] exceptionList = { "a", "an", "the", "in", "on", "of" };
     private char[] separators = { ' ' };
  
     public string ToProperCase(string title)
     {
        bool isException = false;	
  
        string[] words = title.Split( separators, StringSplitOptions.RemoveEmptyEntries);
        string[] newWords = new string[words.Length];
          
        for (int ctr = 0; ctr <= words.Length - 1; ctr++)
        {
           isException = false;
  
           foreach (string exception in exceptionList)
           {
              if (words[ctr].Equals(exception) && ctr > 0)
              {
                 isException = true;
                 break;
              }
           }
  
           if (! isException)
              newWords[ctr] = words[ctr].Substring(0, 1).ToUpper() + words[ctr].Substring(1);
           else
              newWords[ctr] = words[ctr];	
        }	
        return string.Join(" ", newWords); 			
     }
  }
  // Attempting to load the StringLib.dll assembly produces the following output:
  //    Unhandled Exception: System.BadImageFormatException:
  //                         The format of the file 'StringLib.dll' is invalid.
  

  open System
  
  module StringLib =
      let private exceptionList = [ "a"; "an"; "the"; "in"; "on"; "of" ]
      let private separators = [| ' ' |]
  
      [<CompiledName "ToProperCase">]
      let toProperCase (title: string) =
          title.Split(separators, StringSplitOptions.RemoveEmptyEntries)
          |> Array.mapi (fun i word ->
              if i <> 0 && List.contains word exceptionList then
                  word
              else 
                  word[0..0].ToUpper() + word[1..])
          |> String.concat " "
  
  // Attempting to load the StringLib.dll assembly produces the following output:
  //    Unhandled Exception: System.BadImageFormatException:
  //                         The format of the file 'StringLib.dll' is invalid.
  

  Public Module StringLib
     Private exceptionList() As String = { "a", "an", "the", "in", "on", "of" }
     Private separators() As Char = { " "c }
     
     Public Function ToProperCase(title As String) As String
        Dim isException As Boolean = False	
        
        Dim words() As String = title.Split( separators, StringSplitOptions.RemoveEmptyEntries)
        Dim newWords(words.Length) As String
          
        For ctr As Integer = 0 To words.Length - 1
           isException = False
  
           For Each exception As String In exceptionList
              If words(ctr).Equals(exception) And ctr > 0 Then
                 isException = True
                 Exit For
              End If
           Next
           If Not isException Then
              newWords(ctr) = words(ctr).Substring(0, 1).ToUpper() + words(ctr).Substring(1)
           Else
              newWords(ctr) = words(ctr)	 
           End If	 
        Next	
        Return String.Join(" ", newWords) 			
     End Function
  End Module
  

  The following example uses reflection to load an assembly named StringLib.dll. If the source code is compiled with a .NET Framework 1.1 compiler, a BadImageFormatException is thrown by the Assembly.LoadFrom method.

  using System;
  using System.Reflection;
  
  public class Example
  {
     public static void Main()
     {
        string title = "a tale of two cities";
  //      object[] args = { title}
        // Load assembly containing StateInfo type.
        Assembly assem = Assembly.LoadFrom(@".\StringLib.dll");
        // Get type representing StateInfo class.
        Type stateInfoType = assem.GetType("StringLib");
        // Get Display method.
        MethodInfo mi = stateInfoType.GetMethod("ToProperCase");
        // Call the Display method.
        string properTitle = (string) mi.Invoke(null, new object[] { title } );
        Console.WriteLine(properTitle);
     }
  }
  

  open System.Reflection
  
  let title = "a tale of two cities"
        
  // Load assembly containing StateInfo type.
  let assem = Assembly.LoadFrom @".\StringLib.dll"
  
  // Get type representing StateInfo class.
  let stateInfoType = assem.GetType "StringLib"
  
  // Get Display method.
  let mi = stateInfoType.GetMethod "ToProperCase"
  
  // Call the Display method.
  let properTitle = 
     mi.Invoke(null, [| box title |]) :?> string
  
  printfn $"{properTitle}"
  

  Imports System.Reflection
  
  Module Example
     Public Sub Main()
        Dim title As String = "a tale of two cities"
        ' Load assembly containing StateInfo type.
        Dim assem As Assembly = Assembly.LoadFrom(".\StringLib.dll")
        ' Get type representing StateInfo class.
        Dim stateInfoType As Type = assem.GetType("StringLib")
        ' Get Display method.
        Dim mi As MethodInfo = stateInfoType.GetMethod("ToProperCase")
        ' Call the Display method. 
        Dim properTitle As String = CStr(mi.Invoke(Nothing, New Object() { title } ))
        Console.WriteLine(properTitle)
     End Sub
  End Module
  ' Attempting to load the StringLib.dll assembly produces the following output:
  '    Unhandled Exception: System.BadImageFormatException: 
  '                         The format of the file 'StringLib.dll' is invalid.
  

  To address this exception, make sure that the assembly whose code is executing and that throws the exception, and the assembly to be loaded, both target compatible versions of .NET.

• The components of your application target different platforms. For example, you are trying to load ARM assemblies in an x86 application. You can use the following command-line utility to determine the target platforms of individual .NET assemblies. The list of files should be provided as a space-delimited list at the command line.

  using System;
  using System.IO;
  using System.Reflection;
  
  public class Example
  {
     public static void Main()
     {
        String[] args = Environment.GetCommandLineArgs();
        if (args.Length == 1) {
           Console.WriteLine("\nSyntax:   PlatformInfo <filename>\n");
           return;
        }
        Console.WriteLine();
  
        // Loop through files and display information about their platform.
        for (int ctr = 1; ctr < args.Length; ctr++) {
           string fn = args[ctr];
           if (! File.Exists(fn)) {
              Console.WriteLine("File: {0}", fn);
              Console.WriteLine("The file does not exist.\n");
           }
           else {
              try {
                 AssemblyName an = AssemblyName.GetAssemblyName(fn);
                 Console.WriteLine("Assembly: {0}", an.Name);
                 if (an.ProcessorArchitecture == ProcessorArchitecture.MSIL)
                    Console.WriteLine("Architecture: AnyCPU");
                 else
                    Console.WriteLine("Architecture: {0}", an.ProcessorArchitecture);
  
                 Console.WriteLine();
              }
              catch (BadImageFormatException) {
                 Console.WriteLine("File: {0}", fn);
                 Console.WriteLine("Not a valid assembly.\n");
              }
           }
        }
     }
  }
  

  open System
  open System.IO
  open System.Reflection
  
  let args = Environment.GetCommandLineArgs()
  
  if args.Length = 1 then
      printfn "\nSyntax:   PlatformInfo <filename>\n"
  else
      printfn ""
      // Loop through files and display information about their platform.
      for i = 1 to args.Length - 1 do
          let fn = args[i]
          if not (File.Exists fn) then
              printfn $"File: {fn}"
              printfn "The file does not exist.\n"
          else
              try
                  let an = AssemblyName.GetAssemblyName fn
                  printfn $"Assembly: {an.Name}"
                  if an.ProcessorArchitecture = ProcessorArchitecture.MSIL then
                      printfn "Architecture: AnyCPU"
                  else
                      printfn $"Architecture: {an.ProcessorArchitecture}"
                  printfn ""
  
              with :? BadImageFormatException ->
                  printfn $"File: {fn}"
                  printfn "Not a valid assembly.\n"
  

  Imports System.IO
  Imports System.Reflection
  
  Module Example
     Public Sub Main()
        Dim args() As String = Environment.GetCommandLineArgs()
        If args.Length = 1 Then
           Console.WriteLine()
           Console.WriteLine("Syntax:   PlatformInfo <filename> ")
           Console.WriteLine()
           Exit Sub
        End If
        Console.WriteLine()
        
        ' Loop through files and display information about their platform.
        For ctr As Integer = 1 To args.Length - 1
           Dim fn As String = args(ctr)
           If Not File.Exists(fn) Then
              Console.WriteLine("File: {0}", fn)
              Console.WriteLine("The file does not exist.")
              Console.WriteLine()
           Else
              Try
                 Dim an As AssemblyName = AssemblyName.GetAssemblyName(fn)
                 Console.WriteLine("Assembly: {0}", an.Name)
                 If an.ProcessorArchitecture = ProcessorArchitecture.MSIL Then
                    Console.WriteLine("Architecture: AnyCPU")
                 Else
                    Console.WriteLine("Architecture: {0}", an.ProcessorArchitecture)
                 End If
              Catch e As BadImageFormatException
                 Console.WriteLine("File: {0}", fn)
                 Console.WriteLine("Not a valid assembly.\n")
              End Try
              Console.WriteLine()
           End If
        Next
     End Sub
  End Module
  

• Reflecting on C++ executable files may throw this exception. This is most likely caused by the C++ compiler stripping the relocation addresses or the .Reloc section from the executable file. To preserve the .relocation address in a C++ executable file, specify /fixed:no when linking.

BadImageFormatException uses the HRESULT COR_E_BADIMAGEFORMAT, which has the value 0x8007000B.

For a list of initial property values for an instance of BadImageFormatException, see the BadImageFormatException constructors.

Constructors

BadImageFormatException()	Initializes a new instance of the BadImageFormatException class.
BadImageFormatException(SerializationInfo, StreamingContext)	Obsolete. Initializes a new instance of the BadImageFormatException class with serialized data.
BadImageFormatException(String, Exception)	Initializes a new instance of the BadImageFormatException class with a specified error message and a reference to the inner exception that is the cause of this exception.
BadImageFormatException(String, String, Exception)	Initializes a new instance of the BadImageFormatException class with a specified error message and a reference to the inner exception that is the cause of this exception.
BadImageFormatException(String, String)	Initializes a new instance of the BadImageFormatException class with a specified error message and file name.
BadImageFormatException(String)	Initializes a new instance of the BadImageFormatException class with a specified error message.

Properties

Data	Gets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception)
FileName	Gets the name of the file that causes this exception.
FusionLog	Gets the log file that describes why an assembly load failed.
HelpLink	Gets or sets a link to the help file associated with this exception. (Inherited from Exception)
HResult	Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception)
InnerException	Gets the Exception instance that caused the current exception. (Inherited from Exception)
Message	Gets the error message and the name of the file that caused this exception.
Source	Gets or sets the name of the application or the object that causes the error. (Inherited from Exception)
StackTrace	Gets a string representation of the immediate frames on the call stack. (Inherited from Exception)
TargetSite	Gets the method that throws the current exception. (Inherited from Exception)

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetBaseException()	When overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions. (Inherited from Exception)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetObjectData(SerializationInfo, StreamingContext)	Obsolete. Sets the SerializationInfo object with the file name, assembly cache log, and additional exception information.
GetType()	Gets the runtime type of the current instance. (Inherited from Exception)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns the fully qualified name of this exception and possibly the error message, the name of the inner exception, and the stack trace.

Events

SerializeObjectState

Obsolete. Occurs when an exception is serialized to create an exception state object that contains serialized data about the exception. (Inherited from Exception)

See also

• Exception
• Handling and Throwing Exceptions