The ConnectionString option in appsettings.json file giving parse error after deployed under IIS - asp.net-core-mvc

Question

I am working on an ASP.NET Core MVC project. In appsettings.json file, I have the following connection string:
{
"Logging": {
"LogLevel": {
"Default": "Warning"
}
},
"AllowedHosts": "*",
"ConnectionStrings": {
"LabConnectionString": "Server=1234-98761\SQLEXPRESS;Database=db;Trusted_Connection=True;MultipleActiveResultSets=true;",
"providerName": "System.Data.SqlClient"
}
}
It is working fine when the project is executed from Visual Studio. But when it is deployed in the IIS server after compiling, I am getting the following error found in a log file:
Unhandled Exception: System.FormatException: Could not parse the JSON file. Error on line number '9': '"ConnectionStrings": {
"LabConnectionString": "data source=1234-98761;initial catalog=db;Trusted_Connection=True;MultipleActiveResultSets=true;",'.
Newtonsoft.Json.JsonReaderException: Bad JSON escape sequence: \S. Path 'ConnectionStrings.LabConnectionString', line 9, position 52.
Thanks

Answer 1

Just add double back slashes\\ before SQLEXPRESS. Update your code like below:-
"LabConnectionString": "Server=1234-98761\\SQLEXPRESS;Database=db;Trusted_Connection=True;MultipleActiveResultSets=true;",
and your startup.cs file:-
services.AddControllers().AddNewtonsoftJson()
Hope It will resolve your issue.

Answer 2

In JSON format, inside a string the backslash character is used as escape for other special character, and for itself too.
Here is a self explanatory image from Douglas Crockford's and ECMA's JSON specs
So, you have to escape the backslash:
{
"Logging": {
"LogLevel": {
"Default": "Warning"
}
},
"AllowedHosts": "*",
"ConnectionStrings": {
"LabConnectionString": "Server=1234-98761\\SQLEXPRESS;Database=db;Trusted_Connection=True;MultipleActiveResultSets=true;",
"providerName": "System.Data.SqlClient"
}
}