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    <p>As an example of the difference between expression and statement in VB, in VB the following generates a compiler error since <code>count += 1</code> increments <code>count</code> by 1, but the whole expression <code>count += 1</code> does not return a result, so it can't be used as a parameter.</p> <pre class="lang-vb prettyprint-override"><code>Dim count As Integer = 0 Console.WriteLine(count += 1) ' compiler error </code></pre> <p>You have to do this instead</p> <pre><code>Dim count As Integer = 0 count += 1 Console.Writeline(count) </code></pre> <p>Of course same applies to using the <code>+=</code> operator on a String.</p> <h3>What does "In VB, a statement cannot just be an expression" mean?</h3> <ul> <li>The VB compiler requires results to be consumed in some assignment or other operation.</li> <li>Because of this an assignment operation in VB does <strong>not</strong> produce a result. If it did the VB compiler would not allow it to stand alone as a statement (the compiler requires results be consumed).</li> <li>Thus assignments in VB can be used as statements, but not as expressions. That is you cannot use an assignment statement as a parameter to a method, or as an intermediate result.</li> <li>In C# an assignment operation <strong>does</strong> produce a value. Thus in order for assignments to stand alone as statements, the compiler does <strong>not</strong> require all results to be consumed.</li> <li>The corollary in C# is that any other operation that produces a result can stand alone as a statement. <code>2 + 2</code> for instance produces the result <code>4</code> and can stand alone as a statement, whereas in VB it can't.</li> </ul> <h3>Simplified answer to "Why are pre and post increment operators not available in VB?"</h3> <p><code>count++</code> says, <strong>first</strong> return the value of <code>count</code>, <strong>then</strong> increment <code>count</code> (and do not return the value of the assignment to <code>count</code>).<br> In this case the incremented value is not used (the value before incrementing is used). As mentioned before, the VB compiler requires you use or assign values of operations.</p> <p><code>++count</code> says, <strong>first</strong> increment <code>count</code>, <strong>then</strong> return the value of the assignment to <code>count</code>.<br> In this case, the value of assigning +1 to <code>count</code> is returned as the value of the expression. As mentioned before, assignments in VB do not produce a result.<br> Thus there would be some serious pain implementing these operators in VB.</p>
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