设计器中未处理的异常

如何解决设计器中未处理的异常

我在 Visual Studio 2019 中创建了一个项目，该项目在名为 Home 的表单中有多个用户控件。

一切顺利，直到今天。重建我的项目后 Home 表单显示错误提示

The control system.windows.forms.form has thrown an unhandled exception in the designer and has been desabled. 
Exception :
An attempt to attach an auto-named database for file c:\program files(x86)\Microsoft Visual Studio\2019\Enterprise\common7\ide\database\pharmacy.mdf Failed. A database with the same name exists,or specified file cannot be opened,or it is located on unc share.

我检查了连接代码，看起来没问题。但错误仍未解决。

代码：

sqlConnection con = new sqlConnection(@"Data Source=LocalDB)\MSsqlLocalDB;AttachDbFilename=D:\Final Project BCA\PharmacyManagementSystemCSharp\Database\pharmacy.mdf;Integrated Security=True");
con.open()
String str = "Select max(id) from supp;";
sqlCommand cmd = new sqlCommand(str,con);
sqlDataReader dr = cmd.ExecuteReader();
if (dr.Read())
{
String val = dr[0].ToString();
if (val == "")
{
.....
}
private void button1_Click(object sender,EventArgs e)
{
sqlConnection con = new sqlConnection(@"Data Source= (LocalDB)\MSsqlLocalDB;AttachDbFilename=D:\Final Project BCA\PharmacyManagementSystemCSharp\Database\pharmacy.mdf;Integrated Security=True");
            con.open();
            try
            {
                String str = "Insert into supp(name,email,mobile,addr,s_code) values('" + Sup_Name.Text + "','" + Sup_Email.Text + "','" + Sup_Mobile.Text + "','" + Sup_Add.Text + "','" + Sup_Code.Text + "');";
                sqlCommand cmd = new sqlCommand(str,con);
                cmd.ExecuteNonQuery();
                String str1 = "select max(ID) from supp;";
                sqlCommand cmd1 = new sqlCommand(str1,con);
                sqlDataReader dr = cmd1.ExecuteReader();
                if (dr.Read())
                {
                    MessageBox.Show("Inserted supplier Data SuccessFully..");
                    using (sqlConnection con1 = new sqlConnection(@"Data Source=(LocalDB)\MSsqlLocalDB;AttachDbFilename=D:\Final Project BCA\PharmacyManagementSystemCSharp\Database\pharmacy.mdf;Integrated Security=True"))
                    {
                        String str2 = "Select * from supp";
                        sqlCommand cmd2 = new sqlCommand(str2,con1);
                        sqlDataAdapter sda = new sqlDataAdapter(cmd2);
                        DataTable dt = new DataTable();
                        sda.Fill(dt);
                        supplierDataGV.DataSource = new BindingSource(dt,null);
                    }
                    Sup_Name.Text = "";
                    Sup_Code.Text = "";
                    Sup_Email.Text = "";
                    Sup_Mobile.Text = "";
                    Sup_Add.Text = "";

                }
            }
            catch (sqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }