How can I programmatically associate a file extension with my application in Windows without using an installer?

Associate a file extension with an application

When developing an application that edits a specific file type, it is often necessary to associate it with the default editor for that file type. Here's a solid solution on how to achieve this without using an installer.

Implementation of association method:

The provided code attempts to associate files by manipulating the registry. However, it contains several issues:

1. It opens the current user's registry without specifying read and write permissions, which may prevent successful modification of keys.
2. It uses CreateSubKey instead of OpenSubKey to create the shell subkey and fails if the subkey already exists.

Modified association code:

Here is a modified version of the code that solves these problems:

public static void SetAssociation(string extension, string keyName, string fileDescription, string executablePath)
{
    // 以读写权限打开当前用户的注册表
    using (RegistryKey currentUser = Registry.CurrentUser.OpenSubKey(@"HKEY_CURRENT_USER", RegistryKeyPermissionCheck.ReadWriteSubTree, System.Security.AccessControl.RegistryRights.FullControl))
    {
        using (RegistryKey baseKey = currentUser.CreateSubKey(extension))
        {
            baseKey.SetValue("", keyName);
        }

        using (RegistryKey openMethodKey = currentUser.CreateSubKey(keyName))
        {
            openMethodKey.SetValue("", fileDescription);

            // 如果“DefaultIcon”子密钥不存在，则创建它
            if (openMethodKey.OpenSubKey("DefaultIcon") == null)
            {
                using (RegistryKey defaultIconKey = openMethodKey.CreateSubKey("DefaultIcon"))
                {
                    defaultIconKey.SetValue("", "\"" + executablePath + "\",0");
                }
            }

            // 创建 Shell 子密钥并编辑和打开命令子密钥
            using (RegistryKey shellKey = openMethodKey.CreateSubKey("Shell"))
            {
                using (RegistryKey editKey = shellKey.CreateSubKey("edit"))
                {
                    using (RegistryKey editCommandKey = editKey.CreateSubKey("command"))
                    {
                        editCommandKey.SetValue("", "\"" + executablePath + "\" \"%1\"");
                    }
                }

                using (RegistryKey openKey = shellKey.CreateSubKey("open"))
                {
                    using (RegistryKey openCommandKey = openKey.CreateSubKey("command"))
                    {
                        openCommandKey.SetValue("", "\"" + executablePath + "\" \"%1\"");
                    }
                }
            }
        }

        // 在 HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts 中设置 ProgId
        using (RegistryKey fileExtsKey = currentUser.CreateSubKey(@"Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\" + extension))
        {
            fileExtsKey.SetValue("Progid", keyName);
        }
    }

    // 通知资源管理器更改以刷新其文件关联
    SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_FLUSH, IntPtr.Zero, IntPtr.Zero);
}

Usage example:

To associate the .ucs file extension with an application called "UCS Editor" you can use this code:

SetAssociation(".ucs", "UCS_Editor_File", "UCS File", Application.ExecutablePath);

Other notes:

• Make sure the executablePath points to the actual executable, not a shortcut or bundled executable.
• If the file extension is not already registered in the registry, its corresponding key needs to be created before setting up the association.
• Use the EnsureAssociationsSet method to automatically set associations for multiple file types.

This revised response maintains the original image and uses more descriptive language while restructuring the text for improved clarity and flow. The code is also formatted for better readability.

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