Technical Interview Questions

All methods marked with the DllImport attribute must be marked as public static extern.

Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited.

You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.

Here’s a quick example of the DllImport attribute in action:
using System.Runtime.InteropServices; \
class C
{
[DllImport(\"user32.dll\")]
public static extern int MessageBoxA(int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, \”Hello World!\”, \”Caption\”, 0);
}
}
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared [...]

You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}

[Obsolete] public int Foo() {…}
or
[Obsolete(\"This is a message describing why this method is obsolete\")] public int Foo() {…}
Note: The O in Obsolete is always capitalized.

Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
using System;
[assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.

In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If [...]