How to know a class's lowest base is some type

For exmaple, have a type A, how can 开发者_如何学PythonI know one of its ancester is Windows.Forms.Form?

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You can use the IsSubclassOf method on Type:

var myType = typeof(Form1);
var formType = typeof(Form);

Console.WriteLine(myType.IsSubclassOf(formType)); //outputs 'true'

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Something like this (untested):

var x = yourValue;
var t = x.GetType();
var p = t;
while (p.BaseType != null) 
{
  p = t.BaseType;
}

If you're looking for a specific type, rather than just wondering what the base is, you test for it.

var myX = x as WhateverType;
if (myX != null)
{
  // Use myX
}

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In .NET, it's "lowest ancestor" will always be the universal base class, Object. Can you rephrase your question?

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Here is one shortcut for checking for an ancestor relationship between types. That is, A is derived from Form if a variable of type Form can refer to A:

Type aType=typeof(A);

...
bool isFormAnAncestorOfA = typeof(Form).IsAssignableFrom(aType);