More code related to this StackOverflow question: http://stackoverflow.com/questions/20412783/why-is-a-property-get-considered-ambiguous-when-the-other-interface-is-set-only/20426619

base example

interface IGetMethod { int GetValue(); }

interface ISetMethod { void SetValue(int value); }

interface IBothMethods : IGetMethod, ISetMethod { }

class BothMethods : IBothMethods
{
    int _value;

    public int GetValue() { return _value; }
    public void SetValue(int value) { _value = value; }
}

class Test {
    void DoTest(IBothMethods a) {
        var x = a.GetValue(); // no ambiguity here...
    }
}

explicit interface implementation

interface IGetMethod { int GetValue(); }

interface ISetMethod { void SetValue(int value); }

interface IBothMethods : IGetMethod, ISetMethod { }


class BothMethodsWithExplicit : IBothMethods
{
    int _value;
    int _valueExplicit;

    public int GetValue() { return _value; }
    public void SetValue(int value) { _value = value; }
    
    int IGetMethod.GetValue() { return _valueExplicit; }
    void ISetMethod.SetValue(int value) { _valueExplicit = value; }
}

class Test {
    void DoTest() {
        BothMethodsExplicit a = new BothMethodsExplicit();
        a.SetValue(2);
        IGetMethod getA = a;
        Assert.AreEqual(2, a.GetValue());
        Assert.AreEqual(0, getA.GetValue());
        
        ISetMethod setA = a;
        setA.SetValue(3);
        Assert.AreEqual(3, getA.GetValue());
        Assert.AreNotEqual(a.GetValue(), getA.GetValue());
        
        IBothMethods ia = a;
        Assert.AreNotEqual(a.GetValue(), ia.GetValue());
        Assert.AreEqual(getA.GetValue(), ia.GetValue());
    }
}