public static class GraphQlObjectParser
{
    public static string Parse(string queryType, string queryName, string[] subSelection, object @object = null, string objectTypeName = null)
    {
        var query = queryType + "{" + queryName;

        if (@object != null)
        {
            query += "(";

            if (objectTypeName != null)
            {
                query += objectTypeName + ":" + "{";
            }

            var queryData = string.Empty;
            foreach (var propertyInfo in @object.GetType().GetProperties())
            {
                var value = propertyInfo.GetValue(@object);
                if (value != null)
                {
                    var type = Nullable.GetUnderlyingType(propertyInfo.PropertyType) ?? propertyInfo.PropertyType;
                    var valueQuotes = type == typeof(string) ? """ : string.Empty;

                    var queryPart = char.ToLowerInvariant(propertyInfo.Name[0]) + propertyInfo.Name.Substring(1) + ":" + valueQuotes + value + valueQuotes;
                    queryData += queryData.Length > 0 ? "," + queryPart : queryPart;
                }
            }
            query += (objectTypeName != null ? queryData + "}" : queryData) + ")";
        }

        if (subSelection.Length > 0)
        {
            query += subSelection.Aggregate("{", (current, s) => current + (current.Length > 1 ? "," + s : s)) + "}";
        }

        query += "}";

        return query;
    }
}

var query = GraphQlObjectParser.Parse("query", "users", new[] { "id", "name" });

query{users{id,name}}

var query = GraphQlObjectParser.Parse("query", "user", new[] { "id", "name" }, new User { Id = "1" });

query{user(id:"1"){id,name}}

var query = GraphQlObjectParser.Parse("mutation", "user", new[] { "id", "name" }, new User { Id = "1", Name = "John" }, "data");

mutation{user(data:{id:"1",name:"John"}){id,name}}