Early Visual Basic naming recommendations were based on "System Hungarian". Microsoft even published a list of recommended prefixes, quite remarkable in that the name of the component vendor was even included in the prefix. Like "cbos", the custom ComboBox control published by Sheridan, as opposed to "cbop", published by Pioneer.
System Hungarian has always been rather controversial, with a rich history of failing miserably at keeping up with changes. The naming conventions in the winapi are a good example. Clearly the scheme where the tool vendor name is included has no hope of ever scaling into the future, Visual Basic launched an ecosystem with hundreds of control vendors. A convention that has no hope of ever being used consistently is not a useful convention.
So yes, this was entirely dropped in .NET. CamelCase is used very consistently in the tens of thousands of identifier names in the framework, it has been extraordinarily effective. The rules are spelled out well in the naming guidelines.
Do keep in mind that this is just a guide, you are certainly not required to follow them. The conventions used inside your team always trump whatever a software vendor thinks is useful. It is not like they have a good track record of getting it right :)