Thanks @Verheffen Systems - Admin for providing more details.
As you mentioned we need to migrate database as well as web application, lets look at it step wise:
1). Migrate local SQL Server to Azure SQL Database using DMS:
Tutorial: Migrate SQL Server to Azure SQL Database using DMS
This article provides step by step process of migrating the database from local(on-premise) server to Azure.
2). Once this is done you can try connecting to Azure SQL Database using any tool like SSMS, Azure Data Studio etc. After testing the connection, you can make these db changes in connecting string of your web application accordingly.
3). Then we need to deploy the web application to Azure. Please refer to below article that uses Visual Studio to deploy it on Azure App service.
Quickstart: Deploy an ASP.NET web app
This is again step by step process to deply.
Please let us know if this helps or else we can discuss further on the same.
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