# MultiCAD.NET: Calculating the total length of lines One of the frequently asked questions to our technical support is “How to calculate the sum of line lengths (pipeline sections, elements of wire diagram etc.) in a drawing?” There are many ways to solve this problem, and today we will consider an implementation of the MultiCAD.NET application that sums line lengths in nanoCAD, AutoCAD and ZWCAD. As an example we will calculate the sum of pipe lengths in the water supply scheme with two options to select elements for calculating: user selection and selection by the object filter.

## Calculating the length of lines selected by user

Before we set to work, we need to know what a line in MultiCAD.NET is. The line is a standard primitive like circle, text, spline etc. To represent a line within the drawing database, the `DbLine` class from the `Multicad.DatabaseServices.StandardObjects` namespace is used.
A `DbLine` object has properties that store the first and second points of the line but does not contain the length information. Surely, we could calculate the length by the points coordinates, however it is more efficient to access the line’s geometric representation. The geometry data is stored in the LineSeg3d class object that can be accessed through the `DbLine.Line` property and has the Length property to get the length:

Now let’s consider the first option when the user selects a number of lines for calculating the total length. To provide the user with an ability to select objects the `SelectObjects` method of the `McObjectManager` class is used:

The method prompts the user to select entities on the drawing and writes the IDs of selected objects into the array. But we need to make sure the user has selected only entities of desired type. That is why we filter out only IDs that belong to `DbLine` entities from the set, then get length of each of them and increment the result. Below is the command that implements this procedure:

The same approach works also for polylines that consists of one or more line (or arc) segments. The length of a polyline can be derived similarly to a line by using the geometrical representation class `Polyline3d` that can be accessed for every `DbPolyline` object through the `Polyline` property:

## Automatic calculation of the total lines length

When the drawing contains many elements, it makes sense to select object automatically to avoid user input errors. For this purpose an object filter is used. It selects objects that obey the filter criteria: search area (sheets, layers, documents, regions) and object types.
For example, to filter all lines on the specific layer, the filter with specified layer name is used:

In practice automatic line length calculation is applied commonly for creating a report with a list of pipe types on a water supply scheme. Here is the example scheme: In our example there are two types of water pipes: of PVC and stainless steel. Each type is drawn with lines or polylines on a separate layer: Circuit1 or Circuit2.
The command below creates a text report with listing layer names and total pipe lengths for each of them.

Calculation of the total line lengths and filling up the report are performed in the `getLengthSumByLayer()` method:

As the result of command execution the following report will be added on the drawing: 