You can allow Spread for ASP.NET work as a Web Part in a Microsoft SharePoint environment. To do so, follow these steps:

1. Set the trust level to full. Set the TrustLevel in SharePoint web.config to Full.
2. Mark the Spread DLLs safe in web.config (FarPoint.CalcEngine.dll, FarPoint.Excel.dll and FarPoint.Web.Spread.dll).

This assumes you are using the latest version of SharePoint (WSS or MOSS). For earlier versions of SharePoint you also had the additional step of excluding the fp_client folder from the SharePoint server. This is no longer necessary.

Spread can be used inside the Web Part you are developing.

In earlier versions of the product, the FpSpread.RenderWebPart method was used for the .NET Framework 1.x when you created a Web Part based on Microsoft.SharePoint.WebPartPages.WebPart class. In .NET Framework 2.x, the Web Part becomes part of the framework. If you use the framework WebPart class, System.Web.UI.WebControls.WebParts.WebPart, the FpSpread.RenderWebPart method is no longer needed.

See a good introduction to Web Parts at:

• https://docs.microsoft.com/en-us/visualstudio/sharepoint/creating-web-parts-for-sharepoint?view=vs-2019