如何解决此“无法将类型'object'隐式转换为'Microsoft.Office.Interop.Excel.Worksheet'？

Question

我正在打开一个 CSV 文件进行阅读。我得到了这个错误：

无法将类型“object”隐式转换为“Microsoft.Office.Interop.Excel.Worksheet”。

由于某种原因，这个项目有这个错误，而我的其他必须打开 CSV 文件的项目从来没有这个错误。

我做错了什么？

我的代码：

    public partial class Form1 : Form
    {
        //Define Excel data
        _Application importExcelToDataGridViewApp;
        _Workbook importExcelToDataGridViewWorkbook;
        _Worksheet importExcelToDataGridViewWorksheet;
        string position;
        Microsoft.Office.Interop.Excel.Range importExcelToDataGridViewRange;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog op = new OpenFileDialog();
            op.Title = "Browse for file";
            op.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDoc‌​uments);
            op.Filter = "Excel CSV File(*.csv)|*.csv|";
            op.FilterIndex = 1;


            if (op.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    importExcelToDataGridViewApp = new Microsoft.Office.Interop.Excel.Application();

                    importExcelToDataGridViewWorkbook = importExcelToDataGridViewApp.Workbooks.Open(op.FileName);
                    importExcelToDataGridViewWorksheet = importExcelToDataGridViewWorkbook.ActiveSheet; <-- ERROR HERE
                    importExcelToDataGridViewRange = importExcelToDataGridViewWorksheet.UsedRange;

                    List<string> positionList = new List<string>();

                    for (int i = 2; i <= importExcelToDataGridViewRange.Rows.Count; i++)
                    {
                        string username= importExcelToDataGridViewWorksheet.Cells[i, 1].Value; 
                        int salary= (int)importExcelToDataGridViewWorksheet.Cells[i, 2].Value;
                        dataGridView1.Rows.Add(username, salary);

                    }
                }
                catch (Exception err)
                {
                    ErrorWindow eWindow = new ErrorWindow();
                    eWindow.label4.Text = err.GetType().ToString();
                    eWindow.errorDetails.Text = err.Message;
                    eWindow.ShowDialog();
                }
            }

            
        }
    }

Answer 1

importExcelToDataGridViewWorkbook.ActiveSheet 是 object 类型，而不是 Excel.Worksheet 类型，所以你应该手动转换它：

importExcelToDataGridViewWorksheet = importExcelToDataGridViewWorkbook.ActiveSheet as Microsoft.Office.Interop.Excel.Worksheet;

或

importExcelToDataGridViewWorksheet = (Microsoft.Office.Interop.Excel.Worksheet)importExcelToDataGridViewWorkbook.ActiveSheet;