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

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

  To address this exception, use the version of the tool that corresponds to the version of the .NET Framework 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.

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

  Visual Basic

  ' 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.
  

  C#

  // 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.
  

  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#.

• 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.

• Components have been created using different versions of the .NET Framework. Typically, this exception occurs when an application or component that was developed using the .NET Framework 1.0 or the .NET Framework 1.1 attempts 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 attempts to load an assembly that was developed using the .NET Framework 4. The BadImageFormatException may be reported as a compile-time error, or the exception may be thrown at run time. The following example illustrates this scenario. It defines a StringLib class that has a single member, ToProperCase, and that resides in an assembly named StringLib.dll.

  Visual Basic

  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
  

  C#

  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.
  

  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.

  Visual Basic

  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.
  

  C#

  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);
     }
  }
  

  To address this exception, ensure that the assembly from which the exception is thrown attempts to load an assembly that was developed by using a compatible version of the .NET Framework.

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.

.NET Framework

.NET Framework Client Profile

Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

Other Resources