Question

我在下拉列表中有很多if-else语句选择了更改事件，用于根据当前下拉列表中的值select来填充另一个下拉列表。有没有任何通用的方法来减少这么多if-else语句与任何参数类型.. 这是我的下拉列表选择更改事件的代码

protected void ddlBr1Type_SelectedIndexChanged(object sender, EventArgs e)
{
      if (ddlBr1Type.SelectedValue.ToString() == ValidationFields.FO.ToString())
      {
           ddlBr2Type.DataSource = populateNearByDropdown(ValidationFields.FO.ToString());
           ddlBr2Type.DataBind();
      }
      else if (ddlBr1Type.SelectedValue.ToString() == ValidationFields.FW.ToString())
      {
          ddlBr2Type.DataSource = populateNearByDropdown(ValidationFields.FW.ToString());
            ddlBr2Type.DataBind();

     }
     else if (ddlBr1Type.SelectedValue.ToString() == ValidationFields.UF.ToString())
     {
          ddlBr2Type.DataSource = populateNearByDropdown(ValidationFields.UF.ToString());
            ddlBr2Type.DataBind();
     }
     else if (ddlBr1Type.SelectedValue.ToString() == ValidationTypes.O.ToString())
     {
         ddlBr2Type.DataSource = populateNearByDropdown(ValidationTypes.O.ToString());
            ddlBr2Type.DataBind();
     }
     else if (ddlBr1Type.SelectedValue.ToString() == ValidationTypes.W.ToString())
     {
          ddlBr2Type.DataSource = populateNearByDropdown(ValidationTypes.W.ToString());
            ddlBr2Type.DataBind();
     }
     else if (ddlBr1Type.SelectedValue.ToString() == ValidationTypes.P.ToString())
     {
          ddlBr2Type.DataSource = populateNearByDropdown(ValidationTypes.P.ToString());
            ddlBr2Type.DataBind();
     }
     else if (ddlBr1Type.SelectedValue.ToString() == ValidationTypes.C.ToString())
     {
            ddlBr2Type.DataSource = populateNearByDropdown(ValidationTypes.C.ToString());
            ddlBr2Type.DataBind();
      }

  }

此处ValidationTypes和validationfields是一个枚举，这是PopulateNearbyDropdown方法的代码

   private List<string> populateNearByDropdown(String Item1)
    {
        var MatchedItems =  new List<string>();
        var listofitems = new List<string> { "FO", "FW", "O", "W", "UF" };
        if (listofitems.Any(str => str.Contains(Item1)))
        {
            MatchedItems = new List<string> { Item1, ValidationTypes.P.ToString(), ValidationTypes.C.ToString() };
        }
        else if (Item1 == "P")
        {
            MatchedItems = new List<string> { Item1, ValidationTypes.C.ToString() };            
        }
        else if (Item1 == "C")
        {
            MatchedItems = new List<string> { Item1, ValidationTypes.U.ToString() };
        }
        else if (Item1 == "U"  || Item1 == "FC")
        {
            MatchedItems = new List<string> { Item1 };

        }
        return MatchedItems.ToList();
    }

任何人都会对此有所帮助.. 非常感谢提前...

Answer 1

嗯？

可以明确简化为

{
  ddlBr2Type.DataSource = populateNearByDropdown(ddlBr1Type.SelectedValue.ToString());
  ddlBr2Type.DataBind();
}

除非你想要一些检查（ddlBr1Type有效）。

在那种情况下

{
    var valid = new HashSet<string>{ ValidationFields.FW.ToString(), ..... };
    if (valid.Contains(ddlBr1Type.SelectedValue))
    {
        ddlBr2Type.DataSource = populateNearByDropdown(ddlBr1Type.SelectedValue.ToString());
        ddlBr2Type.DataBind();
    }
}

Answer 2

由于你依赖字符串相等，我认为你根本不需要任何逻辑。这个if语句：

if (ddlBr1Type.SelectedValue.ToString() == ValidationFields.FO.ToString())
{
     ddlBr2Type.DataSource = populateNearByDropdown(ValidationFields.FO.ToString());
     ddlBr2Type.DataBind();
}

可以崩溃到：

ddlBr2Type.DataSource = populateNearByDropdown(ddlBr1Type.SelectedValue.ToString());
ddlBr2Type.DataBind();

所有其他if语句都会消失。

Answer 3

你可以这样做：

ddlBr2Type.DataSource = populateNearByDropdown(ddlBr1Type.SelectedValue.ToString());
ddlBr2Type.DataBind();

...

private List<string> populateNearByDropdown(String Item1)
{
    switch(Item1)
    {
        case "FO":
        case "FW":
        case "O":
        case "W":
        case "UF":
            return new List<string> { Item1, ValidationTypes.P.ToString(), ValidationTypes.C.ToString() };
        case "P":
            return new List<string> { Item1, ValidationTypes.C.ToString() };
        case "C":
            return new List<string> { Item1, ValidationTypes.U.ToString() };
        case "U":
        case "FC":
            return new List<string> { Item1 };
        default:
            return new List<string>();
    }
}

Answer 4

如果我不误读您的代码，应该这样做：

protected void ddlBr1Type_SelectedIndexChanged(object sender, EventArgs e)
{
  ddlBr2Type.DataSource = populateNearByDropdown(ddlBr1Type.SelectedValue.ToString());
  ddlBr2Type.DataBind();
}

Answer 5

ddlBr2Type.DataSource = populateNearByDropdown(ddlBr1Type.SelectedValue.ToString());
ddlBr2Type.DataBind();

Answer 6

您可以使用开关。但是，既然你每次重复比较的正确标准，并假设它不会改变，我只需重写第一种方法：

ddlBr2Type.DataSource = populateNearByDropdown(ddlBr1Type.SelectedValue.ToString());
ddlBr2Type.DataBind();

至于第二个，我会想到一个swtich / case，或者可能是这种类型的值的一些反射（ValidationTypes。[letter] .ToString（），但它不是很稳定所以我不确定

Answer 7

我想是代表检查this出

实现if else语句的通用方法

7 个答案: