如何连接到 Visual Studio 中的访问数据库

Question

i have a hospital solution in visual studio 2019. i have completed the design, i need to connect to a my access database.

i have this code to try to achieve that

try
{
    string constring = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Acer\Desktop\Haigazian\Major_Courses\DataBase\My Project\HospitalDB.accdb";
    OleDbConnection conDataBase = new OleDbConnection(constring);
    String x = textBox1.Text;

    OleDbCommand cmdSelectParcel = new OleDbCommand("Select * from Employee where SSN ='" + x + "'", conDataBase);

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

I also have this at the top of the form using System.Data.OleDb; however, this isn't being used and is greyed out.

Whenever I write OleDbConnection it gives me an error and says

"the type name 'OleDbConnection' could not be found in the namespace 'System.Data.OleDb'. this type has been forwarded to assembly 'System.Data.OleDb, Version=4.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' Consider adding a reference to that assembly"

I have copied the code from another solution file and the System.Data.OleDb works perfectly over there so it must have something to do with my project specifically. I have also tried to add the database access through View>Other Windows>Data Sources but I receive the message

"this window is not supported for the selected project. For steps to enable data binding, please visit: https://aka.ms/WinForms/DataBinding"

and I have checked out the website but I haven't been able to figure out.

Does anyone have any idea how to fix this issue?

Answer 1

You need a reference in your project to System.Data.

Incidentally, once you have that done you need to open the database with..

 conDataBase.Open();

You should also parameterize your query rather than passing in values in the query string to avoid SQL Injection...

 DataTable Employees = new DataTable();
 
 using (OleDbCommand cmdSelectParcel = new OleDbCommand("Select * from Employee where SSN = ?", conDataBase))
 {
     cmdSelectParcel.Parameters.Add("?", OleDbType.VarChar).Value = x;
     Employees.Load(cmdSelectParcel.ExecuteReader());
 }

You'll also need to do something with the data when you get it...

 foreach (DataRow Employee in Employees.rows)
 {
     //Do Something
 }
 

Answer 2

Check that your project actually has a reference to the Microsoft OleDb stuff. eg right click your project in solution explorer and select add->reference->COM then look in the list for your Microsoft OleDB stuff and tick them.