在屬性網格c＃4.0中級聯組合框

Question

我正在構建一系列winforms應用程序，並且我需要在選擇國家城市列表時應該填充一個帶有2個組合“國家和城市”的propertyGrid。

我一直在尋找一個例子但找不到任何例子。

任何地方的任何鏈接或codesnippet？

非常感謝

Answer 1

你需要TypeConverters，一個用於城市，一個用於國家：

public class CountryCity {

  [TypeConverter(typeof(CountryConverter))]
  public string Country { get; set; }

  [TypeConverter(typeof(CityConverter))]
  public string City { get; set; }

  private static List<CountryCity> cityList = new List<CountryCity>();

  static CountryCity() {
    cityList.Add(new CountryCity() { Country = "Germany", City = "Berlin" });
    cityList.Add(new CountryCity() { Country = "Germany", City = "Hamburg" });
    cityList.Add(new CountryCity() { Country = "Germany", City = "Munich" });
    cityList.Add(new CountryCity() { Country = "US", City = "Atlanta" });
    cityList.Add(new CountryCity() { Country = "US", City = "Chicago" });
    cityList.Add(new CountryCity() { Country = "US", City = "Los Angeles" });
    cityList.Add(new CountryCity() { Country = "US", City = "New York" });
  }

  public class CityConverter : TypeConverter {
    public override bool GetStandardValuesSupported(ITypeDescriptorContext context) {
      return true;
    }

    public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context) {
      List<string> cities = new List<string>();

      CountryCity cc = context.Instance as CountryCity;
      if (cc != null) {
        if (cc.Country == null) {
          cities.AddRange(cityList.Select(x => x.City));
        } else {
          cities.AddRange(cityList.Where(x => x.Country == cc.Country)
                                  .Select(y => y.City));
        }
      }
      return new StandardValuesCollection(cities);
    }

    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType) {
      if (sourceType == typeof(string)) {
        return true;
      }
      return base.CanConvertFrom(context, sourceType);
    }

    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value) {
      if (value is string) {
        foreach (CountryCity cc in cityList) {
          if (cc.City == (string)value) {
            return cc.City;
          }
        }
      }
      return base.ConvertFrom(context, culture, value);
    }
  }

  public class CountryConverter : TypeConverter {
    public override bool GetStandardValuesSupported(ITypeDescriptorContext context) {
      return true;
    }

    public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context) {
      List<string> items = cityList.Select(x => x.Country).Distinct().ToList();
      return new StandardValuesCollection(items);
    }

    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType) {
      if (sourceType == typeof(string)) {
        return true;
      }
      return base.CanConvertFrom(context, sourceType);
    }

    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value) {
      if (value is string) {
        foreach (CountryCity cc in cityList) {
          if (cc.Country == (string)value) {
            return cc.Country;
          }
        }
      }
      return base.ConvertFrom(context, culture, value);
    }
  }
}

供測試用：

propertyGrid1.SelectedObject = new CountryCity();

Answer 2

使用1個靜態函數創建一個類國家/地區，以檢索所有已知國家

class Countries
{
 public string Country{get;set;}
 public int CountryId {get;set;}

 public static List<Countries>MyCountries()
 {
  var c1 = new Countries{ Country = "Belgium", CountryId = 1};
  var c2 = new Countries{ Country = "Netherlands", CountryId = 2};

  var result= new List<Countries>();
  result.Add(c1);
  result.Add(c2);

  return result;
 }
}

使用靜態函數創建一個類城市來檢索所有城市，使用另一個靜態函數來搜索第一個函數。

class Cities
{
 public string City{get;set;}
 public int CityId{get;set;}
 public int CountryId{get;set;}

 public static List<Cities>MyCities()
 {
  var c1 = new Cities{ CityId = 1, City= "Antwerp", CountryId = 1};
  var c2 = new Cities{ CityId = 2, City= "Den Haag", CountryId = 2};
  var c3 = new Cities{ CityId = 3, City= "Brussels", CountryId = 1};
  var c4 = new Cities{ CityId = 4, City= "Rotterdam", CountryId = 2};
  var c5 = new Cities{ CityId = 5, City= "Amsterdam", CountryId = 2};
  var c6 = new Cities{ CityId = 6, City= "Hasselt", CountryId = 1};

  var result= new List<Cities>();
  result.Add(c1);
  result.Add(c2);
  result.Add(c3);
  result.Add(c4);
  result.Add(c5);
  result.Add(c6);

  return result;
 }

 public static List<Cities>SelectedCities(int countryId)
 {
  //Linq Example
  var l = MyCities();
  var result = from m in l 
               where m.CountryId = countryId
               select m;
  return result;

  //you also could use a foreach or For loop
  //var l = MyCities();
  //var result = new List<Cities>();
  //foreach(var item in l)
  //{
  // if(item.CountryId == countryId)
  // { 
  //  result.Add(item);
  // }
  // return result;
  }
 }
}

在您的表單或usercontrol中添加以下代碼：

public Form1()
{
 InitializeComponent(); //initialises the component
 PopulateCountryBox();  //populate the combobox
 combobox1.SelectedIndexChanged += combobox1_SelectedIndexChanged; //Create the event          
}

在form_load或其他東西中調用下面的函數來加載CountryBox

private void PopulateCountryBox()
{
 var countryList = new List<Countries>();
 combobox1.DataSource = countryList;
 combobox1.DisplayMember = "Country";
 combobox1.ValueMember = "CountryId"; 
}

代碼下方將處理combobox1 selectedindexChanged事件

private void combobox1_SelectedIndexChanged(object sender, EventArgs e)
{
 var cityList = new List<Cities>(combobox1.SelectedValue);
 combobox2.DataSource = cityList;
 combobox2.DisplayMember = "City";
 combobox2.ValueMember = "CityId"; 
}

我希望這能為您提供一個足夠好的例子，隨時提出更多問題