var workbook = new Workbook();
IWorksheet activeSheet = workbook.ActiveSheet;

//add signature line
ISignatureSetup setup = workbook.Signatures.AddSignatureLine(activeSheet, 100.0, 50.0).Setup;
setup.ShowSignDate = false;
setup.AllowComments = false;
setup.SigningInstructions = "Please check the content before signing.";
setup.SuggestedSigner = "Shinzo Nagama";
setup.SuggestedSignerEmail = "shinzo.nagama@ea.com";
setup.SuggestedSignerLine2 = "Commander (Balanced)";

//save to Excel file
workbook.Save("addsignaturelines.xlsx");

//copy signature line to another range
IRange srcRange = activeSheet.Range["A1:I15"];
IRange destRange = activeSheet.Range["A16:I30"];
srcRange.Copy(destRange);

//duplicate signature line
signature.SignatureLineShape.Duplicate();

//copy signature line to another worksheet
activeSheet.Copy();

//create a new signature line and delete with Signature.Delete
ISignature signatureForTest = newSignatureLine();
signatureForTest.Delete();

//create a new signature line and delete with Shape.Delete
signatureForTest = newSignatureLine();
IShape signatureLineShape = signatureForTest.SignatureLineShape;
signatureLineShape.Delete();

//move signature line
signature.SignatureLineShape.Top += 100;
signature.SignatureLineShape.Left += 50;

//add first signature line
ISignature signatureShinzo = signatures.AddSignatureLine(
    activeSheet, 100.0, 50.0);
ISignatureSetup setup1 = signatureShinzo.Setup;
setup1.ShowSignDate = false;
setup1.AllowComments = false;
setup1.SigningInstructions = "Please check the content before signing.";
setup1.SuggestedSigner = "Shinzo Nagama";
setup1.SuggestedSignerEmail = "shinzo.nagama@ea.com";
setup1.SuggestedSignerLine2 = "Commander (Balanced)";

//add second signature line
ISignature signatureKenji = signatures.AddSignatureLine(
    activeSheet, 100.0, 350.0);
ISignatureSetup setup2 = signatureKenji.Setup;
setup2.ShowSignDate = true;
setup2.AllowComments = true;
setup2.SigningInstructions = "Please check the content before signing!";
setup2.SuggestedSigner = "Kenji Tenzai";
setup2.SuggestedSignerEmail = "kenji.tenzai@ea.com";
setup2.SuggestedSignerLine2 = "Commander (Mecha)";

//list signatures with indexes
for (var i = 0; i < signatures.Count; i++)
{
    var signature = signatures[i];
    //change SuggestedSigner
    if (i == 0)
        signature.Setup.SuggestedSigner = "Shinzo Nagama 123";
    //change SuggestedSignerLine2
    if (i == 1)
        signature.Setup.SuggestedSignerLine2 = "Commander (Mecha 1234)";
}

//create a new workbook
var workbook = new Workbook();

//add signature line
ISignature signature = workbook.Signatures.AddSignatureLine(
    workbook.ActiveSheet, 100.0, 50.0);
ISignatureSetup setup = signature.Setup;
setup.ShowSignDate = true;
setup.AllowComments = true;
setup.SigningInstructions = "<your signing instructions>";
setup.SuggestedSigner = "<signer's name>";
setup.SuggestedSignerEmail = "example@microsoft.com";
setup.SuggestedSignerLine2 = "<signer's title>";

//add signature details
var details = new SignatureDetails
{
    Address1 = "<your address>",
    Address2 = "<address 2>",
    SignatureComments = "Final",
    City = "<your city>",
    StateOrProvince = "<your state or province>",
    PostalCode = "<your postal code>",
    CountryName = "<your country or region>",
    ClaimedRole = "<your role>",
    CommitmentTypeDescription = "Approved",
    CommitmentTypeQualifier = "Final"
};

//initialize certificate
var cert = new X509Certificate2("GcExcelTest.pfx", "test@123");
signature.Sign(cert, "John Williams", details);

//save to an excel file to commit signatures
workbook.Save("digitalsignatures.xlsx");

//create a new workbook
var workbook = new Workbook();

//add non visible signatures
ISignature signature = workbook.Signatures.AddNonVisibleSignature();
var details = new SignatureDetails
{
    Address1 = "<your address>",
    Address2 = "<address 2>",
    SignatureComments = "Final",
    City = "<your city>",
    StateOrProvince = "<your state or province>",
    PostalCode = "<your postal code>",
    CountryName = "<your country or region>",
    ClaimedRole = "<your role>",
    CommitmentTypeDescription = "Approved",
    CommitmentTypeQualifier = "Final"
};

var cert = new X509Certificate2("GcExcelTest.pfx", "test@123");
signature.Sign(cert, details);

//save to an excel file
workbook.Save("nonvisiblesignatures.xlsx");

//open a digitally signed workbook
workbook.Open("signsignaturelines.xlsx");

//modify the worksheet
workbook.Worksheets[0].Range["A1"].Value = "Modified";

//countersign using same certificate
workbook.Signatures[0].Countersign(cert);

//save to an excel file
workbook.Save("countersign.xlsx");

workbook.Open("signsignaturelines.xlsx");

//use DigitalSignatureOnly mode, because the workbook was already signed.
//if you don't open it with digital signature only mode, 
//all existing signatures will be removed after saving the workbook.
XlsxOpenOptions openOption = new XlsxOpenOptions { DigitalSignatureOnly = true };

//add signature to this workbook
var signature = workbook.Signatures.AddNonVisibleSignature();
signature.Sign(cert, details);

//commit signatures
workbook.Save("AddNonVisibleSignatureToSignedWorkbook.xlsx");

//create a new workbook
var workbook = new Workbook();
workbook.Open("digitalsignatures.xlsx");
ISignatureSet signatures = workbook.Signatures;

bool signed = false;
bool valid = false;
X509Certificate2 certificate = null;

// Verify signature
foreach (var signature in signatures)
{
    if (signature.IsSigned)
    {
        signed = true;
        certificate = signature.Details.SignatureCertificate;
        valid = signature.IsValid;
        break;
    }
}

// Verify certificate
if (certificate != null)
{
    var status = X509ChainStatusFlags.NoError;

    // build the certificate chain
    var chain = new X509Chain();
    bool certValid = chain.Build(certificate);

    // inspect the results
    if (!certValid)
    {
        var chainStatus = chain.ChainStatus;
        for (var i = 0; i < chainStatus.Length; i++)
        {
            status |= chainStatus[i].Status;
        }
    }

    // Extract the certificate verification result
    var isCertificateExpired = status.HasFlag(X509ChainStatusFlags.NotTimeValid);
    var isCertificateRevoked = status.HasFlag(X509ChainStatusFlags.Revoked);
    var isCertificateUntrusted = status.HasFlag(X509ChainStatusFlags.UntrustedRoot);

    Console.WriteLine("Expired:" + isCertificateExpired);
    Console.WriteLine("Revoked:" + isCertificateRevoked);
    Console.WriteLine("UnTrusted:" + isCertificateUntrusted);
}

//create a new workbook
var workbook = new Workbook();

// This file contains 1 signed signature line and
// a not signed signature line.
workbook.Open("signsignaturelines.xlsx");

//use DigitalSignatureOnly mode, because the workbook was already signed
XlsxOpenOptions openOption = new XlsxOpenOptions { DigitalSignatureOnly = true };

//remove signature of signed signature line
foreach (var signature in workbook.Signatures)
{
    if (signature.IsSignatureLine && signature.IsSigned)
    {
        //remove digital signature.
        //the signature line will not be removed from the SignatureSet
        //in digital signature only mode.
        //because signature lines are shapes
        signature.Delete();
        break;
    }
}

//commit signatures
workbook.Save("deletesignaturefromsignatureline.xlsx");