Resolving a connection String issue

I have an SQL connection string that gives me an error.

The error is :

System.ArgumentException: 'Keyword not supported: 'allowuservariables'.'

using (SqlConnection con = new SqlConnection())
        {
            con.ConnectionString = "server=localhost;user id=root;database=Phone_diary_project1;allowuservariables=True;persistsecurityinfo=True";
            con.Open();
            using (SqlCommand com = con.CreateCommand())
            {
                com.CommandText = "insert into diary(First," +
                    "Last," +
                    "Mobile," +
                    "Email," +
                    "" +
                    "Category) " +
                    "values(" +
                    "@prm1," +
                    "@prm2," +
                    "@prm3," +
                    "@prm4," +
                    "@prm5) ";
                com.Parameters.Add("@prm1", SqlDbType.VarChar, 50).Value = textBox1.Text;
                com.Parameters.Add("@prm2", SqlDbType.VarChar, 50).Value = textBox2.Text;
                com.Parameters.Add("@prm3", SqlDbType.Int).Value = textBox3.Text;
                com.Parameters.Add("@prm4", SqlDbType.VarChar, 50).Value = textBox4.Text;
                com.Parameters.Add("@prm5", SqlDbType.VarChar, 50).Value = comboBox1.Text;
                com.ExecuteNonQuery();
            }
            con.Close();
        }