在 C# 中传递未知数据类型参数答案

【问题标题】：Passing an unknown datatype parameter in C#在 C# 中传递未知数据类型参数
【发布时间】：2020-09-13 14:26:22
【问题描述】：

我的主程序正在通过另一个类读取电子表格，该类对电子表格的架构（即其中的数据类型）一无所知。我的方法是定义一个定义这些数据类型的电子表格记录，并将该记录作为一个类或结构传递给被调用的类以执行此电子表格读取。

问题是 C# 编译器抱怨它不能将 main 的 SpreadsheetRecord 数据类型隐式转换为被调用类已知的数据类型。当然不能，因为目标类对此数据类型一无所知。那么应该如何将电子表格的模式传递给负责读取和保存电子表格数据的类例程呢？

void class Main
{
    public class SpreadsheetRecord
    {
        public double volAvg;
        public double volOvr10;
        public double sumScore;
    }

    static string[] sheetHeads = { "Volume (10 Day Avg)", "Volume (Today/Avg 10 Day)",
            "Equity Summary Score from StarMine from Refinitiv" };

    SpreadsheetData sheetDat = new SpreadsheetData(new SpreadsheetRecord(), sheetHeads);
    ...
}


public class SpreadsheetData //SpreadsheetData parses an "unknown" spreadsheet.xls file
{
    public Dictionary<string, Record> SheetDB { get; private set; } //declaration of database
    public class Record { };  //schema for incoming spreadsheet data record

    public SpreadsheetData(Record schemaRecord, string[] recordHeadings) //constructor read in spreadsheet
    {
        ...
        using (IExcelDataReader excelReader = ExcelReaderFactory.CreateBinaryReader(sheetInputFile.OpenRead()))
        {...
            FieldInfo[] recordFieldInfo = typeof(Record).GetFields();
            for (int i = 1; i < result.Tables[0].Rows.Count; i++)
            {
                for (int j = 0; j < recordHeadings.Length; j++)
                    recordFieldInfo[j].SetValue(schemaRecord, sheet1.Rows[i][Column2RecordCrossIndx[j]]);
                SheetDB.Add(sheet1.Rows[i][indxOfSymbol].ToString(), schemaRecord); //store sheet data record
            }
            ...
        }
    }
}

【问题讨论】：

我认为使该类成为通用类并传递记录的类型（SpreadsheetRecord）应该可以。 public class SpreadsheetData<T> where T : class
您可以按照上面的说明进行通用化。 This 。但我认为你得到的错误是因为Types 你的SpreadsheetData 接受与Types 你正在传递。可能是更改类型 public static dynamic Cast(dynamic obj, Type castTo) { return Convert.ChangeType(obj, castTo); } 如 This

标签： c# class reflection parameter-passing generic-programming

【解决方案1】：

好吧，使用泛型类似乎可以将未知数据类型（即数据库记录）导入电子表格读取类。谢谢一堆。欢迎任何其他建议。

void class Main
{
    public class SpreadsheetRecord
    {
        public double volAvg;
        public double volOvr10;
        public double sumScore;
    }

    static string[] sheetHeads = { "Volume (10 Day Avg)", "Volume (Today/Avg 10 Day)",
            "Equity Summary Score from StarMine from Refinitiv" };

    SpreadsheetData<SpreadsheetRecord> sheetDat = new SpreadsheetData<SpreadsheetRecord>(sheetHeads);
    ...
}


public class SpreadsheetData<T> where T : new() //SpreadsheetData parses an "unknown" spreadsheet.xls file
{
    public Dictionary<string,T> SheetDB { get; private set; } //allow read access to database

    public SpreadsheetData<T>(string[] recordHeadings) //constructor to read in spreadsheet
    {
        ...
        using (IExcelDataReader excelReader = ExcelReaderFactory.CreateBinaryReader(sheetInputFile.OpenRead()))
        {...
            SheetDB = new Dictionary<string,T>(sheet1.Rows.Count); //create database instance
            T schemaRecord = new T(); //create database record instance

            FieldInfo[] recordFieldInfo = typeof(T).GetFields();
            for (int i = 1; i < result.Tables[0].Rows.Count; i++)
            {
                for (int j = 0; j < recordHeadings.Length; j++)
                    recordFieldInfo[j].SetValue(schemaRecord, sheet1.Rows[i][Column2RecordCrossIndx[j]]);
                SheetDB.Add(sheet1.Rows[i][indxOfSymbol].ToString(), schemaRecord); //store sheet data record
            }
            ...
        }
    }
}

【讨论】：