Security :: Encrypting With An X509 Certificate.

I have created an x590 certificate that is in the file :
"C:UsersmartinAppDataRoamingMicrosoftSystemCertificatesMyCertificates"

I am trying to acces the public key to encrypt some plain text.

The system is throwing an "System.ArgumentOutOfRangeException" at the line

Dim certificate As X509Certificate2 = certificateCollection(0)

Can anyone tell me where I am going wrong or tell me another way to access the public key

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This is the complete code:
Imports System.Security
Imports System.Security.Cryptography.X509Certificates
Imports System.Security.Cryptography.X509Certificates.X509Certificate2
Imports System.Security.Cryptography.Pkcs
Partial Class encryptwithcertificare
Inherits System.Web.UI.Page
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim encoding As UTF8Encoding = New UTF8Encoding
Dim cleartext As String = Textbox1.Text
Dim myStore As X509Store = New X509Store()
myStore.Open(OpenFlags.ReadOnly)
Dim certificateCollection As X509Certificate2Collection = myStore.Certificates.Find(X509FindType.FindBySubjectName, "bobby", True)
Dim certificate As X509Certificate2 = certificateCollection(0)
Dim code() As Byte = EncryptwithCertificate(cleartext, certificate)
Label1.Text = Convert.ToBase64String(code)
End Sub
Shared Function EncryptwithCertificate(ByVal cleartext As Byte, ByVal certificate As X509Certificate2) As Byte()
Dim encoding As UTF8Encoding = New UTF8Encoding
Dim cleartextsbyte() As Byte = encoding.GetBytes(cleartext)
Dim contentinfo As ContentInfo = New ContentInfo(cleartextsbyte)
Dim envelopedCms As EnvelopedCms = New EnvelopedCms(contentinfo)
Dim recipient As CmsRecipient = New CmsRecipient(certificate)
envelopedCms.Encrypt(recipient)
Return envelopedCms.Encode()
End Function
End Class