Why Decrypt Excel Worksheet?

To protect our Excel file data information, we can encrypt Excel worksheet by setting password. But we may sometimes forget the password and we can't read the excel data information neither. So, if this happens we need decrypt Excel worksheet. It’s not easy to decrypt Excel Worksheet which has been encrypted because the reason why we encrypt it is to prevent it from reading by people without password. And now, we do not have password.

How to Use C#/VB.NET to Decrypt Excel Worksheet?

Spire.XLS for .NET, a .NET Excel component which enables .NET applications to fast generate, read, write and modify Excel document without Microsoft Office Excel Automation can help us decrypt Excel worksheet by using C#/VB.NET.

Spire.XLS for .NET presents a very easy solution for developers/programmers decrypting Excel worksheet. We just need sheet.Unprotect( "password" ) method and normal encrypted excel worksheet can be decrypted.

Download Spire.XLS for .NET (or Spire.Office) with .NET framework 2.0 (or above) together. The sample code below will show you how to use C#/VB.NET decrypt Excel worksheet through Spire.XLS for .NET.

using Spire.Xls;
namespace DescryptWorksheet
{
    class Program
    {

        static void Main(string[] args)
        {
            Workbook workbook = new Workbook();
            workbook.LoadFromFile("test.xls");
            Worksheet sheet = workbook.Worksheets[0];
            sheet.Unprotect("password");
            workbook.SaveToFile("result.xls", ExcelVersion.Version97to2003);

        }
    }
}

Spire.XLS allows users to operate Excel document directly such as save to stream, save as web response, copy, lock/unlock worksheet, set up workbook properties, etc. As a professional .NET Excel component, it owns the ability of inserting content into Excel document, formatting cells and converting Excel documents to popular office file formats. Spire.XLS for .NET supports Excel 97-2003, Excel 2007 and Excel 2010.

When sharing Excel files with other people or sending files out of your organization, you may want to protect sensitive data from being changed, moved, or deleted. The easiest way to prevent accidental or deliberate changes in the contents is to restrict editing on a worksheet or password protect an entire workbook. In this article, you will learn how to protect and unprotect a workbook or a worksheet in C# and VB.NET using Spire.XLS for .NET.

• Password Protect an Entire Workbook
• Protect a Worksheet with a Specific Protection Type
• Allow Users to Edit Ranges in a Protected Worksheet
• Lock Specific Cells in a Worksheet
• Unprotect a Password Protected Worksheet
• Remove or Reset Password of an Encrypted Workbook

Install Spire.XLS for .NET

To begin with, you need to add the DLL files included in the Spire.XLS for .NET package as references in your .NET project. The DLL files can be either downloaded from this link or installed via NuGet.

PM> Install-Package Spire.XLS

Password Protect an Entire Workbook in C# and VB.NET

By encrypting an Excel document with a password, you ensure that only you and authorized individuals can read or edit it. The following are the steps to password protect a workbook using Spire.XLS for .NET.

• Create a Workbook object.
• Load an Excel file using Workbook.LoadFromFile() method.
• Protect the workbook using a password using Workbook.Protect() method.
• Save the workbook to another Excel file using Workbook.SaveToFile() method.

using Spire.Xls;

namespace PasswordProtectWorkbook
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Workbook object
            Workbook workbook = new Workbook();

            //Load an Excel file
            workbook.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.xlsx");

            //Protect workbook with a password
            workbook.Protect("psd-123");

            //Save the workbook to another Excel file
            workbook.SaveToFile("Encrypted.xlsx", ExcelVersion.Version2016);
        }
    }
}

Imports Spire.Xls
 
Namespace PasswordProtectWorkbook
    Class Program
        Shared  Sub Main(ByVal args() As String)
            'Create a Workbook object
            Dim workbook As Workbook =  New Workbook() 
 
            'Load an Excel file
            workbook.LoadFromFile("C:\Users\Administrator\Desktop\sample.xlsx")
 
            'Protect workbook with a password
            workbook.Protect("psd-123")
 
            'Save the workbook to another Excel file
            workbook.SaveToFile("Encrypted.xlsx", ExcelVersion.Version2016)
        End Sub
    End Class
End Namespace

Protect a Worksheet with a Specific Protection Type in C# and VB.NET

If you wish to grant people permission to read your Excel document but restrict the types of modifications they are allowed to make on a worksheet, you can protect the worksheet with a specific protection type. The table below lists a variety of pre-defined protection types under the SheetProtectionType enumeration.

The following are the steps to protect a worksheet with a specific protection type using Spire.XLS for .NET.

• Create a Workbook object.
• Load an Excel file using Workbook.LoadFromFile() method.
• Get a specific worksheet through Workbook.Worksheets[index] property.
• Protect the worksheet with a protection type using Worksheet.Protect(string password, SheetProtectionType options) method.
• Save the workbook to another Excel file using Workbook.SaveToFile() method.

using Spire.Xls;

namespace ProtectWorksheetWithSpecificProtectionType
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Workbook object
            Workbook workbook = new Workbook();

            //Load an Excel file
            workbook.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.xlsx");

            //Get a specific worksheet
            Worksheet worksheet = workbook.Worksheets[0];

            //Protect the worksheet with the permission password and the specific protect type
            worksheet.Protect("psd-permission", SheetProtectionType.None);

            //Save the workbook to another Excel file
            workbook.SaveToFile("ProtectWorksheet.xlsx", ExcelVersion.Version2016);
        }
    }
}

Imports Spire.Xls
 
Namespace ProtectWorksheetWithSpecificProtectionType
    Class Program
        Shared  Sub Main(ByVal args() As String)
            'Create a Workbook object
            Dim workbook As Workbook =  New Workbook() 
 
            'Load an Excel file
            workbook.LoadFromFile("C:\Users\Administrator\Desktop\sample.xlsx")
 
            'Get a specific worksheet
            Dim worksheet As Worksheet =  workbook.Worksheets(0) 
 
            'Protect the worksheet with the permission password and the specific protect type
            worksheet.Protect("psd-permission", SheetProtectionType.All)
 
            'Save the workbook to another Excel file
            workbook.SaveToFile("ProtectWorksheet.xlsx", ExcelVersion.Version2016)
        End Sub
    End Class
End Namespace

Allow Users to Edit Ranges in a Protected Worksheet in C# and VB.NET

In certain cases, you may need to allow users to be able to edit selected ranges in a protected worksheet. The following steps demonstrate how to.

• Create a Workbook object.
• Load an Excel file using Workbook.LoadFromFile() method.
• Get a specific worksheet through Workbook.Worksheets[index] property.
• Specify editable cell ranges using Worksheet.AddAllowEditRange() method.
• Protect the worksheet with a protection type using Worksheet.Protect(string password, SheetProtectionType options) method.
• Save the workbook to another Excel file using Workbook.SaveToFile() method.

using Spire.Xls;

namespace AllowEditRanges
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Workbook object
            Workbook workbook = new Workbook();

            //Load an Excel file
            workbook.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.xlsx");

            //Get the first worksheet
            Worksheet sheet = workbook.Worksheets[0];

            //Add ranges that allow editing
            sheet.AddAllowEditRange("Range One", sheet.Range["A5:A6"]);
            sheet.AddAllowEditRange("Range Two", sheet.Range["A8:B11"]);

            //Protect the worksheet with a password and a protection type
            sheet.Protect("psd-permission", SheetProtectionType.All);

            //Save the workbook to another Excel file
            workbook.SaveToFile("AllowEditRange.xlsx", ExcelVersion.Version2016);
        }
    }
}

Imports Spire.Xls
 
Namespace AllowEditRanges
    Class Program
        Shared  Sub Main(ByVal args() As String)
            'Create a Workbook object
            Dim workbook As Workbook =  New Workbook() 
 
            'Load an Excel file
            workbook.LoadFromFile("C:\Users\Administrator\Desktop\sample.xlsx")
 
            'Get the first worksheet
            Dim sheet As Worksheet =  workbook.Worksheets(0) 
 
            'Add ranges that allow editing
            sheet.AddAllowEditRange("Range One", sheet.Range("A5:A6"))
            sheet.AddAllowEditRange("Range Two", sheet.Range("A8:B11"))
 
            'Protect the worksheet with a password and a protection type
            sheet.Protect("psd-permission", SheetProtectionType.All)
 
            'Save the workbook to another Excel file
            workbook.SaveToFile("AllowEditRange.xlsx", ExcelVersion.Version2016)
        End Sub
    End Class
End Namespace

Unprotect a Password Protected Worksheet in C# and VB.NET

To remove the protection of a password-protected worksheet, invoke the Worksheet.Unprotect() method and pass in the original password as a parameter. The detailed steps are as follows.

• Create a Workbook object.
• Load an Excel file using Workbook.LoadFromFile() method.
• Get a specific worksheet through Workbook.Worksheets[index] property.
• Remove the protection using Worksheet.Unprotect(string password) method.
• Save the workbook to another Excel file using Workbook.SaveToFile() method.

using Spire.Xls;

namespace UnprotectWorksheet
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Workbook object
            Workbook workbook = new Workbook();

            //Load an Excel file containing protected worksheet
            workbook.LoadFromFile(@"C:\Users\Administrator\Desktop\ProtectedWorksheet.xlsx");

            //Get the first worksheet
            Worksheet sheet = workbook.Worksheets[0];

            //Unprotect the worksheet using the specified password
            sheet.Unprotect("psd-permission");

            //Save the workbook to anther Excel file
            workbook.SaveToFile("UnprotectWorksheet.xlsx", ExcelVersion.Version2016);
        }
    }
}

Imports Spire.Xls
 
Namespace UnprotectWorksheet
    Class Program
        Shared  Sub Main(ByVal args() As String)
            'Create a Workbook object
            Dim workbook As Workbook =  New Workbook() 
 
            'Load an Excel file containing protected worksheet
            workbook.LoadFromFile("C:\Users\Administrator\Desktop\ProtectedWorksheet.xlsx")
 
            'Get the first worksheet
            Dim sheet As Worksheet =  workbook.Worksheets(0) 
 
            'Unprotect the worksheet using the specified password
            sheet.Unprotect("psd-permission")
 
            'Save the workbook to anther Excel file
            workbook.SaveToFile("UnprotectWorksheet.xlsx", ExcelVersion.Version2016)
        End Sub
    End Class
End Namespace

Remove or Reset Password of an Encrypted Workbook in C# and VB.NET

To remove or reset password of an encrypted workbook, you can use the Workbook.Unprotect() method and the Workbook.Protect() method, respectively. The following steps show you how to load an encrypted Excel document and delete or change the password of it.

• Create a Workbook object.
• Specify the open password through Workbook.OpenPassword property.
• Load the encrypted Excel file using Workbook.LoadFromFile() method.
• Remove the encryption using Workbook.Unprotect() method. Or change the password using Workbook.Protect() method.
• Save the workbook to another Excel file using Workbook.SaveToFile() method.

using Spire.Xls;

namespace RemoveOrResetPassword
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Workbook object
            Workbook workbook = new Workbook();

            //Specify the open password
            workbook.OpenPassword = "psd-123";

            //Load an encrypted Excel file
            workbook.LoadFromFile(@"C:\Users\Administrator\Desktop\Encrypted.xlsx");

            //Unprotect workbook
            workbook.UnProtect();

            //Reset password
            //workbook.Protect("newpassword");

            //Save the workbook to another Excel file
            workbook.SaveToFile("Unprotect.xlsx", ExcelVersion.Version2016);
        }
    }
}

Imports Spire.Xls
 
Namespace RemoveOrResetPassword
    Class Program
        Shared  Sub Main(ByVal args() As String)
            'Create a Workbook object
            Dim workbook As Workbook =  New Workbook() 
 
            'Specify the open password
            workbook.OpenPassword = "psd-123"
 
            'Load an encrypted Excel file
            workbook.LoadFromFile("C:\Users\Administrator\Desktop\Encrypted.xlsx")
 
            'Unprotect workbook
            workbook.UnProtect()
 
            'Reset password
            'workbook.Protect("newpassword");
 
            'Save the workbook to another Excel file
            workbook.SaveToFile("Unprotect.xlsx", ExcelVersion.Version2016)
        End Sub
    End Class
End Namespace

Apply for a Temporary License

If you'd like to remove the evaluation message from the generated documents, or to get rid of the function limitations, please request a 30-day trial license for yourself.

The most important reason that people lock worksheet when perform tasks in Excel is to protect the original Excel file from editing or modifying by other people. Through Microsoft Excel, you can set the entire Excel worksheet by setting its property as Read Only or just set partial region area cells as Read Only via protecting worksheet. While how to lock worksheet with C#, VB.NET will be the core topic in this section.

Spire.XLS for .NET, as a fast and reliable excel component, enables you to lock your worksheet by setting Worksheet class property: Worksheet.Range.Style.Locked = true. By this component, you can lock any worksheet that you need. In this solution, worksheet one and worksheet two are locked as you view in below picture:

Now, before the detail code, you have to add Spire.Xls dll by download Spire.XLS for .NET.

using Spire.Xls;

namespace lock_excel_worksheet
{
    class Program
    {
        static void Main(string[] args)
        {
            Workbook workbook = new Workbook();
            workbook.LoadFromFile(@"..\lock worksheet.xls");
            workbook.Worksheets[0].Range.Style.Locked = true;
            workbook.Worksheets[1].Range.Style.Locked = true;
            workbook.Worksheets[0].Protect("", SheetProtectionType.All);
            workbook.Worksheets[1].Protect("", SheetProtectionType.All);
            workbook.SaveToFile("result.xls",ExcelVersion.Version97to2003);
        }
    }
}

Imports Spire.Xls

Namespace lock_excel_worksheet
    
    Class Program
        
        Private Shared Sub Main(ByVal args() As String)
            Dim workbook As Workbook = New Workbook
            workbook.LoadFromFile("..\lock worksheet.xls")
            workbook.Worksheets(0).Range.Style.Locked = true
            workbook.Worksheets(1).Range.Style.Locked = true
            workbook.Worksheets(0).Protect("", SheetProtectionType.All)
            workbook.Worksheets(1).Protect("", SheetProtectionType.All)
            workbook.SaveToFile("result.xls",ExcelVersion.Version97to2003)
        End Sub
    End Class
End Namespace

Spire.XLS allows user to operate Excel document directly such as save to stream, save as web response, copy, lock/unlock worksheet, set up workbook properties, etc. As a professional .NET/Silverlight Excel component, it owns the ability of inserting content into Excel document, formatting cells and converting Excel documents to popular office file formats. Spire.XLS for .NET supports Excel 97-2003, Excel 2007 and Excel 2010.

This section aims at providing developers a solution to unlock sheet in Excel workbook with C#, VB.NET via this Excel library Spire.XLS for .NET.

Spire.XLS for .NET enables you to unlock any sheet in Excel file only by one line of key code: Spire.Xls.Worksheet.Unprotect(string password); Besides, as an MS Excel component, Spire.XLS for .NET also enables you to create, read and handle Excel files with fast speed. Below is an Excel file with protected worksheets which will be unlocked in my task.

Since you will use Spire.XLS for .NET, you have to download Spire.XLS for .NET and install it on system. When you create your project, please do not forget to add Spire.XLS.dll as reference from Bin folder. The default path is "..\Spire.XLS\Bin\NET4.0\Spire.XLS.dll". Please note that Spire.XLS for .NET supports .NET Framework 2.0 and above. Here is the whole code for unlocking Excel sheet:

namespace UnlockExcelSheet
{
    class Program
    {
        static void Main(string[] args)
        {
            //initialize an instance of Workbook
            Workbook workbook = new Workbook();
            //Load an Excel file with protected worksheet
            workbook.LoadFromFile(@"..\Unlock Excel Worksheet.xlsx");
            //get the first worksheet
            Worksheet sheet = workbook.Worksheets[0];
            //Unprotect worksheet
            sheet.Unprotect("iceblue");
            //Save the file
            workbook.SaveToFile("Sample.xlsx",ExcelVersion.Version2010);
            //Launch the file
            System.Diagnostics.Process.Start("Sample.xlsx");
        }
    }
}
          

Namespace UnlockExcelSheet
	Class Program
		Private Shared Sub Main(args As String())
			'initialize an instance of Workbook
			Dim workbook As New Workbook()
			'Load an Excel file with protected worksheet
			workbook.LoadFromFile("..\Unlock Excel Worksheet.xlsx")
			'get the first worksheet
			Dim sheet As Worksheet = workbook.Worksheets(0)
			'Unprotect worksheet
			sheet.Unprotect("iceblue")
			'Save the file
			workbook.SaveToFile("Sample.xlsx",ExcelVersion.Version2010)
			'Launch the file
			System.Diagnostics.Process.Start("Sample.xlsx")
		End Sub
	End Class
End Namespace
          

After executing above code, you can see that the protected worksheet in the original Excel file has been unlocked, we can edit it also. Please see following image.

In this section, I have introduced the solution to unlock any sheet in Excel file via Spire.XLS for .NET. I hope it can help you. If you have any questions, feedbacks and advice, you can put them on E-iceblue Forum. We will promise a prompt reply.