I am trying to pass userid and password through the clientContext.Credentials method, but i am getting the below error

```
microsoft.sharepoint.client.clientcontext' does not contain a definition for 'credentials'

```

Below is the code snippet that i am trying to use

```
var ctx = new ClientContext("SITE URL");
ctx.Credentials = new Microsoft.SharePoint.Client.SharePointOnlineCredentials("username", "password");

```

Also, I have included the below namespaces 

```
using Microsoft.SharePoint;
using Microsoft.SharePoint.Client;

```

What have i missed? Why is the `.Credentials` not available?

I am using .Net version 4 for the project