It returns 40 for RC4_40 , 128 for RC4_128 and AES128, 256 for AES256_Weak and AES256. It can be only set for RC4_Custom type of encryption. In that case, its default value is 128. Key must be between 40 and 128 and divisble by 8.

public int KeyLength { get; set; }

Public Property KeyLength As Integer
	Get
	Set

public:
property int KeyLength {
	int get ();
	void set (int value);
}