LINQ查詢具有下拉菜單中的值以與數據進行比較

Question

我的查詢如下。 有人可以幫我如何在Linq語句中添加dbquery嗎？ 有一條注釋“在此處添加”。 從昨天開始我一直在掙扎。 想法是形成LINQ語句並立即獲取列表。 謝謝。

String dbwhere = "";
if (ddlName.SelectedItem.Value != "")
{
    dbwhere = " && (User.Name == '" + ddlName.SelectedItem.Value.TrimEnd() + "')";
}
if (ddlHeightFrom.SelectedItem.Value != "")
{
    dbwhere = dbwhere + " && (Physical.Height >= '" + ddlHeightFrom.SelectedItem.Value.TrimEnd() + "')";
}
if (ddlHeightTo.SelectedItem.Value != "")
{
    dbwhere = dbwhere + " && (Physical.Height <= '" + ddlHeightTo.SelectedItem.Value.TrimEnd() + ")";
}

var usersquery = (
  from physical in dbContext.Physicals
  join user in dbContext.User on physical.UserID equals user.UserID
  join photos in dbContext.Photo on User.UserID equals photos.UserID
  where photos.PhotoNum == 1 && photos.Status == true
  // =======  Add dbwhere here ============
  select new
  {
     photos.PhotoURL,
     photos.PhotoDescription,
     user.State,
     user.Country,
     physical.EyesColor,
     physical.HairColorInfo,
     physical.HairTypeInfo,
     physical.BodyHeight,
     physical.BodyWeight,
  }).ToList();

Answer 1

您可以重寫查詢以避免將linq與SQL混合使用（並使其免受SQL注入的攻擊）

var usersquery = (
    from physical in dbContext.Physicals
    join user in dbContext.User on physical.UserID equals user.UserID
    join photos in dbContext.Photo on User.UserID equals photos.UserID
    where photos.PhotoNum == 1 && photos.Status == true
    select new
    {
        physical,
        user,
        photos,
    }; // do not put ToList here!

現在，您可以添加特殊檢查：

if (ddlName.SelectedItem.Value != "")
{
  var userName = ddlName.SelectedItem.Value.TrimEnd();
  usersquery = usersquery.Where(x => x.user.Name == userName);
}

if (ddlHeightFrom.SelectedItem.Value != "")
{
  var height = int.Parse(ddlHeightFrom.SelectedItem.Value.TrimEnd());
  usersquery = usersquery.Where(x => x.physical.Height >= height);
}

// and so on

現在您可以使用ToList實現數據

var result = usersquery.Select(x => new 
  {
    x.photos.PhotoURL,
    x.photos.PhotoDescription,
    x.user.State,
    x.user.Country,
    x.physical.EyesColor,
    x.physical.HairColorInfo,
    x.physical.HairTypeInfo,
    x.physical.BodyHeight,
    x.physical.BodyWeight
  }).ToList();

注意：我已將其寫在記事本中，因此可能有錯誤。 但是我希望想法很明確