验证签名—什么原因导致“签名无效”错误?

I need to sign and verify a string using my company's digital certificate. The VerifyHash(hash, CryptoConfig.MapNameToOID("SHA1"), signature); portion returns false so I get the "Signature not valid" error. What am I doing wrong? What is the most likely cause for this error?I need to sign and verify a string using my com