# V3003. The use of 'if (A) {...} else if (A) {...}' pattern was detected. There is a probability of logical error presence.

The analyzer has detected a potential error in a construct consisting of conditional statements.

Consider the following example:

    if (a == 1)
      Foo1();
    else if (a == 2)
      Foo2();
    else if (a == 1)
      Foo3();

In this code, the 'Foo3()' method will never get control. We are most likely dealing with a logical error here and the correct version of this code should look as follows:

    if (a == 1)
      Foo1();
    else if (a == 2)
      Foo2();
    else if (a == 3)
      Foo3();

In practice though, errors of this type can take more complicated forms, as shown below.

For example, the analyzer has found the following incorrect construct.

    ....
    } else if (b.NodeType == ExpressionType.Or ||
               b.NodeType == ExpressionType.OrEqual){
                       current.Condition = ConstraintType.Or;
    } else if(...) {
    ....
    } else if (b.NodeType == ExpressionType.OrEqual ||
               b.NodeType == ExpressionType.Or){
                       current.Condition = ConstraintType.Or |
                       ConstraintType.Equal;
    } else if(....

In this example, the uppermost if statement checks the following condition:

    b.NodeType == ExpressionType.Or ||
    b.NodeType == ExpressionType.OrEqual.

while the lowermost if statement checks a condition with the same logic but written in a reverse order, which is hardly noticeable for a human yet results in a runtime error.

    b.NodeType == ExpressionType.OrEqual ||
    b.NodeType == ExpressionType.Or

This diagnostic is classified as:

CWE-570

You can look at examples of errors detected by the V3003 diagnostic.