Question

我有一个抽象数据实体MyDataRow，它继承了DataRowA。有一个泛型类使用它BusinessRow<TData> where TData:MyDataRow。问题是我想要根据字符串变量创建BusinessRow的新对象：
public BusinessRow<MyDataRow> AddNewRow(string rowType)
并在其泛型类型中使用MyDataRow的继承类之一：

public class BusinessRow<TData>
    where TData : MyDataRow
{
}

public abstract class MyDataRow
{
}

public class DataRowA : MyDataRow
{
}

public class Main
{
    public BusinessRow<MyDataRow> AddNewRow(string rowType)
    {
        BusinessRow<MyDataRow> row = null;
        switch (rowType)
        {
            case "A":
            default:

                row =new BusinessRow<DataRowA>();
// Error CS0029  Cannot implicitly convert type 
// 'BusinessRow<DataRowA>' to 'BusinessRow<MyDataRow>' 

                break;
        }
        return row;
    }
}

在以下代码中

BusinessRow<MyDataRow> row = new BusinessRow<DataRowA>();

我收到此错误

Error CS0029  Cannot implicitly convert type 
 'BusinessRow<DataRowA>' to 'BusinessRow<MyDataRow>'

隐式转换Generic Class的类型为其Specific继承

0 个答案: