System.Data.SqlClient.SqlException: Login failed for user

Solution 1:

Just set Integrated Security=False and it will work ,according to a comment difference between True and False is:

True ignores User ID and Password if provided and uses those of the running process, SSPI(Security Support Provider Interface ) it will use them if provided which is why MS prefers this. They are equivalent in that they use the same security mechanism to authenticate but that is it.

Solution 2:

Assuming you're intending to use Windows Authentication to impersonate the service account, you have to set up Windows Authentication in both IIS and ASP.NET.

In IIS, make sure that the Windows Authentication module is added and enabled. Also make sure your application pool is running under a domain account, not a local account.

In ASP.NET make sure the authentication mode attribute is set to "Windows"

<system.web>
    <authentication mode="Windows"/>
 </system.web>

Solution 3:

I had similar experience and it took me time to solve the problem. Though, my own case was ASP.Net MVC Core and Core framework. Setting Trusted_Connection=False; solved my problem.

Inside appsettings.json file

"ConnectionStrings": {
    "DefaultConnection": "Server=servername; Database=databasename; User Id=userid; Password=password; Trusted_Connection=False; MultipleActiveResultSets=true",
  },

Solution 4:

You can also get this error if your SQL Server has not been configured to use Mixed mode authentication - it doesn't actually tell you that this is not enabled!