C#反射 字符串转为实体类，并做为参数传入泛型方法中使用

工作中有这样一个需求，有N张不同的报表，每张报表对应一个数据源，统计数据采用内存方式，首先在内在里定义了数据源对应实体。统计条件用lamdba表达式式实现，通过工具对单元格进行定义。在实现过程中针对每一张表来写取数显示是很Low的了，取数条件定义都是规则的，统计实现就是一段C#代码，但是要针对不同的数据源也就是不同的List<Entity>，通过研究发现通过泛型和反射可以实现。

根据字符串获取实体类型

private Type getEntity(string typeName)
{
    var workPath = AppDomain.CurrentDomain.BaseDirectory;
    string[] files = Directory.GetFiles(workPath, "XXX.Utils.dll", SearchOption.TopDirectoryOnly);
    foreach (string file in files)
    {
        string ext = file.Substring(file.LastIndexOf("."));
        if (ext != ".dll") continue;
        try
        {
            Assembly asm = Assembly.LoadFile(file);
            Type[] allTypes = asm.GetTypes();
            foreach (Type t in allTypes)
            {
                if (t.IsSubclassOf(typeof(XXDataRecord)))
                {
                    if (t.Name.ToUpper().IsSame(typeName.ToUpper()))
                        return t;
                }
            }
        }
        catch
        {
            return null;
        }
    }
    return null;
}

泛型方法定义

public XXDataMemory BuildDataMemoryPattern<T>(XXParams zb, string id) where T : XXDataRecord, new()

调用方法代码

var obj = new GenerateDataHelper(_Param);
Type myGenericClassType = obj.GetType();
//MakeGenericMethod 设置泛型参数类型
MethodInfo mi = myGenericClassType.GetMethod("BuildDataMemoryPattern").MakeGenericMethod(typeEntity);
int count = 0;
//设置调用方法参数
object[] invokeArgs = new object[] { zb, id, count };
//调用
var dt = (DataTable)mi.Invoke(obj, invokeArgs);
//获取回返数据
recordCount = (int)invokeArgs[9];

下面是全部代码，具体功能实现略过

public class UtilFetchHelper 
{
    //获取实体类型
    private Type getEntity(string typeName)
    {
        var workPath = AppDomain.CurrentDomain.BaseDirectory;
        string[] files = Directory.GetFiles(workPath, "XXX.Utils.dll", SearchOption.TopDirectoryOnly);
        foreach (string file in files)
        {
            string ext = file.Substring(file.LastIndexOf("."));
            if (ext != ".dll") continue;
            try
            {
                Assembly asm = Assembly.LoadFile(file);
                Type[] allTypes = asm.GetTypes();
                foreach (Type t in allTypes)
                {
                    if (t.IsSubclassOf(typeof(XXDataRecord)))
                    {
                        if (t.Name.ToUpper().IsSame(typeName.ToUpper()))
                            return t;
                    }
                }
            }
            catch
            {
                return null;
            }
        }
        return null;
    }

    public DataTable BuildDataMemoryPattern(XXParams zb, string id, out int recordCount)
    {
        //根据传入参数获取实体名称
        var entityName = GetDataSourceEntityName(zb);
        //获取实体类型
        Type typeEntity = getEntity(entityName);
        if (typeEntity == null)
            return  null;
        var obj = new GenerateDataHelper(_Param);
        Type myGenericClassType = obj.GetType();
        MethodInfo mi = myGenericClassType.GetMethod("BuildDataMemoryPattern").MakeGenericMethod(typeEntity);
        int count = 0;
        object[] invokeArgs = new object[] { zb, id, count };
        var dt = (DataTable)mi.Invoke(obj, invokeArgs);
        //这里获取回返数据
        recordCount = (int)invokeArgs[9];
        return dt;
    }
}

public class GenerateDataHelper
{
    private List<XXDataRecord> _DataList;
    private List<XXDataRecord> DataList
    {
        set { _DataList = value; }
        get { return _DataList; }
    }    
    
    private List<T> GetDataSource<T>() where T : XXDataRecord, new()
    {
        var _DataList = new List<T>();
        var dt = DB.ExecuteDataTable("Select * From XX");
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            var dataEnt = new T();
            for (int j = 0; j < dt.Columns.Count; j++)
            {
                dataEnt[dt.Columns[j].ColumnName] = dt.Rows[i][j];
            }
            _DataList.Add(dataEnt);
        }
        return _DataList;        
     }
        
        
    public XXDataMemory BuildDataMemoryPattern<T>(XXParams zb, string id) where T : XXDataRecord, new()
    {
        List<T> DataList = new List<T>();
        DataList = GetDataSource<T>();
        //以下是具体实现代码 针对DataList查询操作
    }
}