Building ETABSSharp: A C# Wrapper for the ETABS API

The ETABS API is powerful. It exposes almost everything — model geometry, load cases, analysis results, design checks. But working with it directly is painful.

Methods are stringly typed. There’s no IntelliSense guidance on what parameters mean. Error handling is COM-era ref parameters. You end up writing the same boilerplate fifty times per script.

ETABSSharp is a C# wrapper that fixes this.

The problem with the raw API

Here’s a typical raw ETABS API call to get story drift results:

// Raw ETABS API — what you normally write
int numberResults = 0;
string[] storyName = Array.Empty<string>();
string[] loadCase = Array.Empty<string>();
string[] stepType = Array.Empty<string>();
double[] stepNum = Array.Empty<double>();
double[] driftX = Array.Empty<double>();
double[] driftY = Array.Empty<double>();

int ret = model.Results.StoryDrifts(
    ref numberResults,
    ref storyName,
    ref loadCase,
    ref stepType,
    ref stepNum,
    ref driftX,
    ref driftY
);

if (ret != 0) throw new Exception("Failed to get story drifts");

That’s 15 lines to get one result table. The ref arrays are pre-allocated by the API — there’s no type safety on what you pass in, and if ret != 0 you get no information about what went wrong.

The ETABSSharp approach

With ETABSSharp, the same operation becomes:

// ETABSSharp — what you write instead
var drifts = await etabs.Results.StoryDriftsAsync();

foreach (var drift in drifts)
{
    Console.WriteLine($"{drift.Story} | {drift.LoadCase} | DX: {drift.DriftX:F4}");
}

Strongly typed. Async-capable. drift.Story gives you IntelliSense. If the API call fails, you get a proper exception with a message.

Architecture decisions

1. Thin wrapper, not an abstraction

ETABSSharp wraps the ETABS COM API — it doesn’t try to replace it. Every method maps 1:1 to an ETABS API call. This means:

• The full API surface is available
• Behaviour is predictable — if ETABS does it, ETABSSharp can do it
• No magic or hidden logic

2. Result types instead of ref parameters

Every output is a strongly typed record:

public record StoryDrift(
    string Story,
    string LoadCase,
    string StepType,
    double StepNum,
    double DriftX,
    double DriftY
);

3. Fluent access pattern

var etabs = await ETABSSharp.Connect();

// Navigate to what you need
var frameForces = await etabs
    .Results
    .FrameForces(loadCase: "1.2D + 1.6L");

The AI layer

The real reason I built ETABSSharp isn’t just the cleaner API — it’s what the clean API enables: an MCP server that lets AI assistants talk to ETABS directly.

More on that in the next post.

Get it

• GitHub: github.com/tadoEng/etabssharp
• NuGet: dotnet add package ETABSSharp

If you’re automating ETABS with C# and you have questions, open an issue or reach out. I use this in production work every week.