'ColConfigSubsystem.Database.GetChromeMakeByYear（int）'的最佳重載方法匹配有一些無效參數

Question

我在C＃中有一個事件，它使用來自不同數據庫的關聯值填充類文件（database.cs）中的下拉列表通過上面提到的類文件中包含的oracle存儲過程。這是我目前使用的代碼：

///<summary> 
    ///Populates the model dropdownlist with available chrome data associated with 
    ///the year selected 
    /// </summary> 
    private void PopulateChromeModel() 
    { 
     //define a counter 
     int itemCounter = 1; 

     //create a database object 
     Database cmake = new Database(); 

     //call GetChromeMakeByYear to retrieve the available models according to 
     //the year 
     DataTable table = cmake.GetChromeMakeByYear(ddlVehicleYear.SelectedItem); 

     Trace.Write("populating models"); 

     //create a flag showing whether an item should be selected. Preset it to false 
     bool selected = false; 

     //we may need to select, then later deselect, an item based on the model. 
     int selectedItemByModel = 0; 

     //preset the current selected code to "" 
     string currentSelectedCode = ""; 

     //define a flag to indicate whether we've already selected an item. Preset it to false. 
     bool hasSelected = false; 

     //create a list item for the 0 position 
     ListItem firstItem = new ListItem("-- SELECT --", ""); 

     //first see if there is a currently selected item. If so, set the current selected model. 
     //this is done because we have to clear all of the selected items before adding the new list. 
     //but we want to be able to select the model that is already selected. 
     if (ddlVehicleModel.SelectedIndex > 0) 
     { 
      currentSelectedCode = ddlVehicleModel.SelectedValue; 
     } 

     //clear any items from the list 
     ddlVehicleModel.Items.Clear(); 

     //add the first item 
     ddlVehicleModel.Items.Add(firstItem); 

     //loop through the table and add items for each row. 
     foreach (DataRow row in table.Rows) 
     { 
      //get this record's chrome id 
      string id = row["CHROME_ID"].ToString(); 

      //get this record's make 
      string make = row["CHROME_MAKE"].ToString(); 

      //set a flag specifying whether the item should be selected based on year 
      bool selectBasedOnYear = false; 

      if (currentSelectedCode == id) 
      { 
       selected = true; 
      } 
      else 
      { 
       selected = false; 
       selectBasedOnYear = false; 
      } 

      Trace.Write(string.Format("{0}: {1}: {2}: {3}", id, make, selected, selectBasedOnYear)); 

      //create a new list item for this model 
      ListItem newItem = new ListItem(id, make); 

      //if we have thrown either selected flag and we have not already selected an item, 
      //mark this option as selected 
      if ((selected || selectBasedOnYear) && !hasSelected) 
      { 
       Trace.Write("-- Either selected or selectedBasedOnYear was true, and hasSelected was false"); 

       //first make sure the first item is deselected 
       firstItem.Selected = false; 
       Trace.Write("-- deselected the first item."); 

       //next deselect and items that were selected due to year. This allows the user selected 
       //region to override the default model for year. 
       if (selectBasedOnYear != null) 
       { 
        Trace.Write(string.Format(" -- deselecting item {0}, which was selected due to year", selectBasedOnYear)); 
        ddlVehicleMake.Items[selectedItemByModel].Selected = false; 
       } 

       //select this item 
       newItem.Selected = true; 
       Trace.Write(" -- selected the current item"); 

       //only throw the hasSelected flag if this was a user-selected region 
       if (selected) 
       { 
        hasSelected = true; 
        Trace.Write(" -- set hasSelected to true"); 
       } 

      } 

      //add the model to the list 
      ddlVehicleMake.Items.Add(newItem); 

      itemCounter++; 
     } 

     //if there's no items selected and we have more than just the default item, 
     //default to the first item 
     if (ddlVehicleMake.Items.Count > 0 && !hasSelected && selectedItemByModel == 0) 
     { 
      ddlVehicleMake.SelectedIndex = 1; 
     } 
    } 

的錯誤是在下面的行拋出：

 //call GetChromeMakeByYear to retrieve the available models according to 
     //the year 
     DataTable table = cmake.GetChromeMakeByYear(ddlVehicleYear.SelectedItem); 

我已經包括了我的在線評論和總結，以幫助這個事件的範圍。我不太確定錯誤的原因是什麼。

Answer 1

您需要將值取消整數。

DataTable table = cmake.GetChromeMakeByYear((int)ddlVehicleYear.SelectedItem); 

當項目從他們在對象的形式獲取的，因爲你可以存儲任何類型中數據的下拉列表檢索。編譯器不知道你在列表中指定的項目實際上是一個整數（而不是一個字符串），所以不知道你試圖調用哪個函數。

更多拆箱和拳擊在這裏：http://msdn.microsoft.com/en-us/library/yz2be5wk.aspx

Answer 2

試試這個：

DataTable table = cmake.GetChromeMakeByYear((int) ddlVehicleYear.SelectedValue);