UpdateAccessKeyResponse

The following command deactivates the specified access key (access key ID and secret access key) for the IAM user named Bob.

To activate or deactivate an access key for an IAM user

var client = new AmazonIdentityManagementServiceClient();
var response = client.UpdateAccessKey(new UpdateAccessKeyRequest 
{
    AccessKeyId = "AKIAIOSFODNN7EXAMPLE",
    Status = "Inactive",
    UserName = "Bob"
});