Excel沒有使用oledb C＃的更新值

Question

我是C＃的新手，正嘗試使用OLEDB將值寫入Excel文件。 這里的問題是，第一次在該位置沒有excel文件，它可以正常工作並將其打印到excel，但是第二次，如果存在excel，它不會覆蓋或向excel寫新值。 我還需要循環運行此程序，因為我要打印四行而不是一行。 需要幫助。

這是我的代碼片段，我知道我只有一行要打印的代碼，但是我不知道添加循環的位置：

            try
        {

            var connectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyLearn\ExcelWorkBook.xls;Extended Properties=Excel 8.0";
            var sqlText = "CREATE TABLE TimeData ([HH] INT, [MM] INT,[AM / PM] VARCHAR(10))";

            using (var excelConnection = new OleDbConnection(connectionString))
            {


                // data is an object so it works with DBNull.Value
                object HHValue = TimeInHH.Text;
                object MMValue = TimeInMM.Text;
                object AMPMValue = Combo1AMPM.Text;




                // Executing this command will create the worksheet inside of the workbook
                // the table name will be the new worksheet name
                using (var command = new OleDbCommand(sqlText, excelConnection))
                {
                    if (excelConnection.State != ConnectionState.Open) {
                        excelConnection.Open();
                        command.ExecuteNonQuery();
                    }
                }

                // Add (insert) data to the worksheet
                var commandText = $"Insert Into TimeData ([HH], [MM], [AM / PM]) Values (@PropertyOne, @PropertyTwo, @PropertyThree)";

                using (var command = new OleDbCommand(commandText, excelConnection))
                {
                    // We need to allow for nulls just like we would with
                    // sql, if your data is null a DBNull.Value should be used
                    // instead of null 
                    command.Parameters.AddWithValue("@PropertyOne", HHValue ?? DBNull.Value);
                    command.Parameters.AddWithValue("@PropertyTwo", MMValue ?? DBNull.Value);
                    command.Parameters.AddWithValue("@PropertyThree", AMPMValue ?? DBNull.Value);
                    command.ExecuteNonQuery();
                }
            }


        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception: " + ex.Message);
        }
        finally
        {
            Console.WriteLine("Executing finally block.");
        }

這是我正在從中捕獲數據的屏幕，並希望在單擊“提交”按鈕時在excel上打印。

Answer 1

您需要檢查表是否已經存在 ，如果是，則只需添加記錄即可。

這是一個有效的例子

        try
        {
            var connectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyLearn\ExcelWorkBook.xls;Extended Properties=Excel 8.0";

            var sqlText = "CREATE TABLE TimeData ([HH] INT, [MM] INT,[AM / PM] VARCHAR(10))";

            using (var excelConnection = new OleDbConnection(connectionString))
            {
                object HHValue = TimeInHH.Text;
                object MMValue = TimeInMM.Text;
                object AMPMValue = Combo1AMPM.Text;

                // Executing this command will create the worksheet inside of the workbook
                // the table name will be the new worksheet name
                using (var command = new OleDbCommand(sqlText, excelConnection))
                {
                    if (excelConnection.State != ConnectionState.Open)
                    {
                        excelConnection.Open();
                        //check if table already exists.
                        var exists = excelConnection.GetSchema("Tables", new string[4] { null, null, "TimeData", "TABLE" }).Rows.Count > 0;

                        if(!exists)
                           command.ExecuteNonQuery();
                    }
                }

                // Add (insert) data to the worksheet
                var commandText = $"Insert Into TimeData ([HH], [MM], [AM / PM]) Values (@PropertyOne, @PropertyTwo, @PropertyThree)";

                using (var command = new OleDbCommand(commandText, excelConnection))
                {
                    // We need to allow for nulls just like we would with
                    // sql, if your data is null a DBNull.Value should be used
                    // instead of null 
                    command.Parameters.AddWithValue("@PropertyOne", HHValue ?? DBNull.Value);
                    command.Parameters.AddWithValue("@PropertyTwo", MMValue ?? DBNull.Value);
                    command.Parameters.AddWithValue("@PropertyThree", AMPMValue ?? DBNull.Value);
                    command.ExecuteNonQuery();
                }
            }


        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception: " + ex.Message);
        }
        finally
        {
            Console.WriteLine("Executing finally block.");
        }

    }