Check value from one table in sql and if exists then increment the value in other table

Hi, I need some help with asp.net, ado.net & sql
I have 2 sql tables. One stores the book information and other table stores the number of copies. what i want is, I want to first check if the book of same name is already present and if book is already present then it should increment the values in copy column of copies table.

for example, first table contains books information with columns like its name,publisher,edition and second table has name and number of copies. so when I add any book information, then it should check booktable based on book name and if same book is present then it should increment value in copies table. this is what i have written but its not working

SqlConnection additemconn = new SqlConnection(strconn);
            additemconn.Open();
            SqlCommand checkcomm = new SqlCommand("if EXISTS(select Bname from Books where Bname='" + txtItemname.Text + "') Update Bookcopies set BooksCopies=BooksCopies + 1 where Bname='" + txtItemname.Text + "' End if");
            checkcomm.Connection = additemconn;
            checkcomm.ExecuteNonQuery();
            
            
            SqlConnection additemconnadd = new SqlConnection(strconn);
            additemconn.Open();
            SqlCommand additemcomm = new SqlCommand("Insert into Books values ('" + txtItemname.Text + "','" + txtitemauthor.Text + "','" + lstitemflagged.Text + "','" + txtitempublisher.Text + "','" + txtitemedition.Text + "','" + txtitemdate.Text + "','" + txtItemId.Text + "') ");
            
            additemcomm.Connection = additemconnadd;
            additemcomm.ExecuteNonQuery();