C# translator problem

Hello everyone,
Im new to programming and spending a lot of time trying things like a translator.
I've been working on this translator in C# the last few hours, using the Bing API and it works for translating english to dutch. but i've got a problem:

Now, I want to use radiobuttons to let the user choose the language,
and this is the problem:

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strTranslatedText = client.Translate("BBB3D27FD8F14CC7E38AF6F8B41096120A546B5E", txtTranslate.Text, "nl", "en");

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Can I tie "nl" and "en" to a function or something that enables the user to change "nl" and/or "en" in that line by clicking the radiobuttons.

something like this:

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string nl = 0;
string en = 1;

txtTranslate.Text, "0", "1");

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how should I do this?