在緊湊框架中動態增長和縮小DataGrid？

Question

我在Compact Framework中有一個DataGrid我需要填充數以萬計的記錄，這證明是一個問題，因爲當我嘗試時，內存不足。

有沒有辦法動態地只顯示和加載用戶正在查看的行，而不是一次性將所有行轉儲到網格中？

Answer 1

下面的代碼將自動調整其數據源爲數組的數據網格的列寬。

public static void AutosizeColumnsWithArray(DataGrid grid, PaintEventArgs e) 
    { 
     Font dataFont = grid.Font; 
     Font headerFont = GetHeaderFont(dataFont); 
     IList list = null; 
     if (grid.DataSource is IList) 
     { 
      list = (IList) grid.DataSource; 
     } 
     else if (grid.DataSource is IListSource) 
     { 
      list = ((IListSource) grid.DataSource).GetList(); 
     } 

     if (list == null || list.Count < 0) 
     { 
      return; 
     } 

     if (grid.TableStyles.Count == 0) 
     { 
      return; 
     } 

     var pdc = TypeDescriptor.GetProperties(list[0]); 
     var dataGridTableStyle = new DataGridTableStyle(); 
     dataGridTableStyle.MappingName = GetMappingName(list); 
     int totalWidth = 0; 

     for (int i = 0; i < pdc.Count; i++) 
     { 
      var columnName = pdc[i].Name; 

      bool validColumn = grid.TableStyles[0].GridColumnStyles.Contains(columnName); 
      if (!validColumn) 
      { 
       continue; 
      } 

      var gridColumnStyle = grid.TableStyles[0].GridColumnStyles[columnName]; 
      var indexToEdit = grid.TableStyles[0].GridColumnStyles.IndexOf(gridColumnStyle); 

      var headerText = grid.TableStyles[0].GridColumnStyles[columnName].HeaderText; 
      var maxSize = e.Graphics.MeasureString(headerText, headerFont); 
      int maxLength = headerText.Length; 

      int rowCount = 0; 
      const int maxRowsToCompare = 200; 
      foreach (object o in list) 
      { 
       if (rowCount == maxRowsToCompare) 
       { 
        break; 
       } 
       object result = pdc[i].GetValue(o); 

       string value = result == null ? string.Empty : result.ToString().Trim(); 

       if (ValueCannotBeLongest(value, maxLength)) 
       { 
        rowCount++; 
        continue; 
       } 

       SizeF size = e.Graphics.MeasureString(value, dataFont); 
       if (size.Width > maxSize.Width) 
       { 
        maxSize = size; 
        maxLength = value.Length; 
       } 
       rowCount++; 
      } 
      var newWidth = (int) (maxSize.Width + 5); 
      grid.TableStyles[0].GridColumnStyles[indexToEdit].Width = newWidth; 
      totalWidth += newWidth; 
     } 
    } 

    private static bool ValueCannotBeLongest(string value, int maxLength) 
    { 
     return (value.Length == 0) || (value.Length + 3 < maxLength); 
    } 

    private static string GetMappingName(IList list) 
    { 
     string result; 

     if (list is ITypedList) 
     { 
      result = ((ITypedList) list).GetListName(null); 
     } 
     else 
     { 
      result = list.GetType().Name; 
     } 

     return result; 
    } 

    private static Font GetHeaderFont(Font dataFont) 
    { 
     string FontName = dataFont.Name; 
     float FontSize = dataFont.Size; 
     return new Font(FontName, FontSize, FontStyle.Bold); 
    }