Learning LabVIEW (Part 3) - A change in concepts

   The code given in "Learning LabVIEW (II) - Operating .NET Generic Classes"  yesterday is actually wrong. According to our assumption, Add is called first to put the Key-Value pair "eleven"-11 into the Dictionary, and then TryGetValue is called to find the Value corresponding to Key: "eleven". So the query must be successful. However, when executing yesterday's code repeatedly, the query fails occasionally, as shown in the figure below: Key: "eleven" has been added using Add, why does the query fail sometimes? The reason is that we use the wrong concept to write LabVIEW programs.  Traditional computer languages ​​are essentially written with the flow of instructions as the core, and the written codes are executed one by one in sequence. However, graphical programming languages ​​such as LabVIEW and Simulink construct programs with the flow of data as the core. When the program is constructed with the flow of data as the core, sometimes the execution order of instructions is not so obvious, and some instructions are even automatically executed in parallel without knowing it. I have consulted NI's customer service about this point, and they have clearly stated that the LabVIEW runtime will automatically use multi-threading to process functions that can be executed in parallel without user intervention. This is a very good feature, and it is also very consistent with the characteristics of graphical programming, which is centered on data flow.  However, when we draw LabVIEW programs with the previous concept of programming centered on instructions, we will make mistakes unconsciously. The code segment for writing and querying Dictionary yesterday is shown in the figure below: It seems that Add is executed before TryGetValue if it is executed from left to right. This is actually because the way the graphics are drawn confuses us. If we simply adjust the position of each node, as shown in the figure below: LabVIEW, which is centered on data flow, will not necessarily execute which function first. If TryGetValue is executed first, the query will fail.  How should this problem be solved now? LabVIEW's programming concept centered on data flow makes automated parallel programming possible on the one hand, and on the other hand, makes "sequential execution" a structure that requires explicit declarations; this is very different from traditional languages. Traditional languages ​​write code line by line, and are executed line by line, which is naturally a sequential structure.  We found the tool for representing sequential structures in the Programming column of the toolbox: use this flat sequential structure to frame the part that needs to precede the TryGetValue call, as shown in the figure below: In this way, the data will continue to flow down only after all the actions in the box are executed, so there will be no more query failures.