Edit: You are using UTF-16 in C#, you must use same encoding in both languages:
Node.js:
var crypto = require("crypto");
var sha256 = crypto.createHash("sha256");
sha256.update("ThisPassword", "utf8");//utf8 here
var result = sha256.digest("base64");
console.log(result); //d7I986+YD1zS6Wz2XAcDv2K8yw3xIVUp7u/OZiDzhSY=
C#:
SHA256 sha256 = SHA256Managed.Create(); //utf8 here as well
byte[] bytes = sha256.ComputeHash(Encoding.UTF8.GetBytes("ThisPassword"));
string result = Convert.ToBase64String(bytes);
Console.WriteLine(result); //d7I986+YD1zS6Wz2XAcDv2K8yw3xIVUp7u/OZiDzhSY=