将if-chain转换为基于规则的字典

Question

我坚持将一个巨大的if-chain转换成字典.在传统解决方案中,Excel导出如下所示:

foreach (DataRow dr in fullData.Rows)
{
    DataRow newRow = dt.NewRow();

    foreach (DataColumn dc in dt.Columns)
    {
        String s = dc.Caption;

        if (s.Equals("ID"))
            newRow[dc] = dr["id"];
        else if (s.Equals("PQ-Nr"))
            newRow[dc] = dr["pqNummer"];
        else if (s.Equals("GJ"))
            newRow[dc] = dr["geschaeftsjahr"];
        else if (s.Equals("Link"))
            newRow[dc] = dr["link"];
        /*more complex example*/
        else if(s.Equals("GF"))
        {
            string content = "";
            int intVal = 0;
            if (Int32.TryParse(dr["id"].ToString(), out intVal))
            {
                List<Freigabe> liste = DBHelper.getFreigabenByPersonalTyp(intVal, Personal.GF);
                foreach (Freigabe f in liste)
                {
                //build content string here
                }
            }
            newRow[dc] = content.TrimEnd();
        }
        /*plus around 60 more else if statements*/
    }
    dt.Rows.Add(newRow);
}
return dt;

我的想法是将规则和分配的实际行分成两部分.所以我创建了一个字典:

var rules = new Dictionary<Func<string, bool>, Func<DataRow, object>>()
{
    {y => y == "ID", x =>  x["id"] },
    {y => y == "PQ-Nr", x => x["pqNummer"] },
    //....
};

为了获得当前列值,我执行以下操作:

foreach (DataRow dr in fullData.Rows)
{
    DataRow newRow = dt.NewRow();

    foreach (DataColumn dc in dt.Columns)
    {
        String s = dc.Caption;

        newRow[dc] = from r in rules
                     where r.Key(s)
                     select r.Value(dr);
    }
    dt.Rows.Add(newRow);
}
return dt;

完成报告中每个单元格的内容现在为:System.Linq.Enumerable+WhereSelectEnumerableIterator2 [System.Collections.Generic.KeyValuePair 2[System.Func2 [System.String,System.Boolean],System.Func 2[System.Data.DataRow,System.Object]],System.Object]而不是其值.

我在这里做错了什么？

Answer 1

我建议改变rules类型:

// No lambdas, just string to string
Dictionary<String, String> rules = new Dictionary<String, String>() {
  {"ID", "id"},
  {"PQ-Nr", "pqNumme"},
  {"GJ", "geschaeftsjahr"},
  {"Link", "link"},
  //TODO: put other rules here
};

所以

foreach (DataRow dr in fullData.Rows) {
    DataRow newRow = dt.NewRow();

    foreach (DataColumn dc in dt.Columns)
        newRow[dc] = dr[rules[dc.Caption]];

    dt.Rows.Add(newRow);
}

编辑:如果没有复杂的规则(如"GF"编辑问题中的一个)Dictionary<String, String> rule也可以帮助:

   foreach (DataColumn dc in dt.Columns) {
     String rule;

     if (rules.TryGetValue(dc.Caption, out rule))
         newRow[dc] = dr[rule]; // <- all the simple rules
     else if (dc.Caption.Equals("GF")) { // <- few specific rules
       ...
     }
   }