Step 1: Click New Project, then select Visual C# on the left, then Windows and then select Windows Forms Application. Name your project "SerialKeyDemo" and then click OK
Step 2: Right click on your project select Manage NuGet Packages -> Search SoftwareProtector -> Install
Software Protector is an open source 100% managed .NET licensing system based on SKGL Project. Generate keys for your software, and validate them using SKGL library in your own project.
Step 3: Design your form as below

Step 4: Add code to button click event handler as below
private void btnGenerate_Click(object sender, EventArgs e)
{
//Generate serial key
SKGL.Generate generate = new SKGL.Generate();
generate.secretPhase = txtPassword.Text;
txtSerial.Text = generate.doKey(Convert.ToInt32(txtDay.Text));
}
private void btnValid_Click(object sender, EventArgs e)
{
//Check valid key
SKGL.Validate validate = new SKGL.Validate();
validate.secretPhase = txtPassword.Text;
validate.Key = txtSerial.Text;
txtStatus.Text = "Creation date: " + validate.CreationDate + "\r\n" + "Expire date: " + validate.ExpireDate + "\r\n" + "Day left: " + validate.DaysLeft;
}
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