c# - 从方法返回 boolean 值

Question

我正在我的程序中创建一个保存选项，将更改保存到一个文件中。我正在使用此代码保存并获取 MessageBox 以显示过程的结果我在此行收到错误消息“未将对象引用设置为对象的实例。”

     SaveFileCheck = StockHandler.SaveChangesToFile();

这是我的代码

    private void Save_Click(object sender, EventArgs e)
    {

        bool SaveFileCheck = false;
        var result = MessageBox.Show("Are you sure you want to Save the changes ?", "My   Application",
      MessageBoxButtons.YesNo, MessageBoxIcon.Asterisk);
        if (result == DialogResult.Yes)
        {           

                 SaveFileCheck = StockHandler.SaveChangesToFile();
                 if (SaveFileCheck)
                 {
                     MessageBox.Show("The process was a success");
                 }
                 else
                 {
                     MessageBox.Show("The process failed please make sure that the file is not been       used and try again");
                 } 

            //Save the file back


        }
    }
}
}

    public bool SaveChangesToFile() 
    {
        try
        {
            if (FileName != null)
            {
                using (StreamWriter Write = new StreamWriter(FileName, false))
                {
                    foreach (Stock s in FileStockList)
                    {
                        Write.Write(s.ToString() + "\r\n");

                    }

                }
            }
            else {
                return false;
            }

        }
        catch(IOException ex) 
        {
            return false;
            throw new ArgumentException("something went wrong an error" + ex + "is been cought");

        }
        return true;


    }

Answer 1

StockHandler 为空。

如果StockHandler 不是static 类，您需要先创建它的一个实例，然后才能调用它的方法:

var handler = new StockHandler();
SaveFileCheck = handler.SaveChangesToFile();

或者，如果 StockHandler 是一个成员变量:

StockHandler = new // something