.NET RSA VerifySignature keeps returning false

Question

In this VB.Net code I sign a test string and then verify the signature. When I use the same cryptoProviderRSA variable for both signing and verifying, the signature is verified successfully. But if I try to create another cryptoProviderRSA variable (it is called cryptoProviderRSA_2 in the code), the VerifySignature keeps returning False. This sample code is pretty simple, yet I don't see what makes cryptoProviderRSA_2 different from cryptoProviderRSA, so the signature verification fails. Any help is appreciated, thanks!

Private Sub SignAndVerifyString(testStringToSign As String)

    '---- sign string 
    Dim testByteArrayToSign As Byte() = Encoding.ASCII.GetBytes(testStringToSign)

    Dim hashAlgorithm As New SHA1Managed
    Dim hashValue As Byte() = hashAlgorithm.ComputeHash(testByteArrayToSign)

    Dim cryptoProviderRSA As New RSACryptoServiceProvider

    Dim signatureFormatterRSA As New RSAPKCS1SignatureFormatter(cryptoProviderRSA)
    signatureFormatterRSA.SetHashAlgorithm("SHA1")

    Dim signatureByteArray As Byte() = signatureFormatterRSA.CreateSignature(hashValue)


    '----- verify string 
    Dim cryptoProviderRSA_2 As New RSACryptoServiceProvider

    '--- When this line is used, VerifySignature below returns True
    Dim signatureDeFormatterRSA As New RSAPKCS1SignatureDeformatter(cryptoProviderRSA)

    '--- When this line is used, VerifySignature below returns False
    'Dim signatureDeFormatterRSA As New RSAPKCS1SignatureDeformatter(cryptoProviderRSA_2)

    signatureDeFormatterRSA.SetHashAlgorithm("SHA1")

    signatureDeFormatterRSA.VerifySignature(hashValue, signatureByteArray)

End Sub