Unicode characters not supported in a SQL database

Question

I am using C# in Visual Studio and I am trying to insert some data into a SQL database. Some unicode characters are turned into question marks when I try to insert them into the db. They appear just fine in the code or in a MessageBox.

For example: ș Ș ț Ț Ă ă Î î are turned to ? ? ? ? A a Î î //romanian characters

Here is the table:

    CREATE TABLE [dbo].[Bookshelf]
(
    [Id] INT NOT NULL PRIMARY KEY IDENTITY(1, 1), 
    [Text] NVARCHAR(50) NOT NULL
)

And here is the code:

private void Form1_Load(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\Comsa\source\repos\Program\Program\Database1.mdf;Integrated Security=True");
            con.Open();

            string value = "ș Ș ț Ț Ă ă Î î";
            SqlCommand cmd = new SqlCommand("INSERT INTO Bookshelf(Text) VALUES('" + value + "')",con);
            cmd.ExecuteNonQuery();
            con.Close();
        }

And this is the output:

My question is what UTF does a SQL database use and if there is a way to insert those characters without altering them.

Answer 1

To send Unicode strings prefix the string with N:

N'This is Unicode'

without the prefix it will be treated by whatever 8bit encoding applies.

Also, using string concatenation to build SQL is a recipe for SQL Injection.