When developing an application, it is often useful to have test data in the tables of your development database. You can then try out your stored procedures or write automated code tests using your sample data. With the SQL Server Object Explorer that is part of the SQL Server Data Tools (SSDT) in Visual Studio 2012, it is easy to enter or edit data into your tables.
See this link for an introduction to SQL Server Object Explorer.
To add data to a table in a SQL Server database using SQL Server Object Explorer:
1) Open the SQL Server Object Explorer toolbox using View | SQL Server Object Explorer from Visual Studio.
2) Drill down to the Databases node, then to your database, then to Tables.
3) Right-click and select View Data.
4) Visual Studio displays the data in an editor for you to review or update.
In this case, the Id column is read-only because it is defined to be an Identity column.
5) Enter any desired data.
Because the Id column is set as an Identity column, it is automatically assigned to the next Id value.
Use the SQL Server Object Explorer any time you want to add or edit data in the tables of your development database.