Why rsacryptoserviceprovider cannot be acquired for the existing key container?

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C#

cryptography

We have CspParameters as

private const string _providerName = "Microsoft Base Smart Card Crypto Provider"
CspParameters cspParameters = new CspParameters();
cspParameters.ProviderName = _providerName;
cspParameters.ProviderType = 1;
cspParameters.KeyContainerName = container;
cspParameters.Flags = CspProviderFlags.UseExistingKey;

These CspParameters are assigned to RSACryptoServiceProvider to create instance of the CSP as

using (RSACryptoServiceProvider rsaProvider = new RSACryptoServiceProvider(cspParameters))
                    {
                        pubKeyXml = rsaProvider.ToXmlString(false);
                    } // using

This function fails to acquire the CSP from the existing key containers. Where am i going wrong ?

What I have tried:

I have tried by changing the flags of the CspParameters. If the flag is set as cspParameters.Flags = CspProviderFlags.UseDefaultKeyContainer; , then it is assuming default container and creating the instance of CSP.