//Authentication
var plainTextBytes = System.Text.Encoding.UTF8.GetBytes("abc:def");
string encodedAuth = System.Convert.ToBase64String(plainTextBytes);
request_.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", encodedAuth);

"securityDefinitions": {
    "basic": {
        "type": "basic",
        "description": "Basic HTTP Authentication"
    }
}, "security": [{
        "basic": []
    }
]