I am new to C#. 
I have a parent class declared:

```
class PmdTable
{
}

```

and I have a child class 

```
class PmdSdStageCfg : PmdTable
{

```

Now it complains if I do like:

```
List<OracleObject.PmdTable> instanceList = new List<PmdSdStageCfg>();

```

I get this error

> 
> Cannot implicitly convert type 'System.Collections.Generic.List' to 'System.Collection.Generics.List'. 
> 
> 
> 

Since PmdTable is the parent class. Why does this not work?