使用Visual Studio在運行時創建本地數據庫

Question

初學者的問題 - 請我可以詢問有關在運行時以編程方式創建本地數據庫文件的建議。我想稍後可以使用Windows資源管理器以與文本和其他文件相同的方式重命名，刪除它們，並將它們複製到其他計算機。

這是使用Visual Studio Community 15與C＃，安裝SQL Server Data Tools 14.0.50616.0。計算機具有的Microsoft SQL Server 2014

對於我已刪除了我的程序留下下面的代碼，它採用了Windows窗體應用程序有3個按鈕（btnCreateDb，btnDeleteDb，並btnDoesDbExist）和組合框的剩餘部分的示例cbxDb爲數據庫名稱。它使數據庫位於現有文件夾C:\DbTemp中。

它會顯然創建並刪除一個新的數據庫並生成文件，例如mydb1.mdf和mydb1.ldf在文件夾中，並聲明它們存在。但是，如果我使用資源管理器刪除這兩個文件，則在嘗試刪除或創建數據庫時會引發異常;和btnDoesDbExist表明它仍然存在。

爲什麼在Windows資源管理器中刪除文件時數據庫仍然顯示存在？ btnDoesDatabaseExist下的代碼沒有引用文件的路徑，所以它必須看到別的東西，但是在哪裏？這是程序用戶創建，刪除和檢測這些數據庫的正確方法嗎？

using System; 
using System.Data; 
using System.Windows.Forms; 

//my additions 
using System.Data.SqlClient; 

namespace DataProg15 
{ 
public partial class Form1 : Form 
{ 
    public Form1() 
    { 
     InitializeComponent(); 
    } 

    public static string form1ConnectionString = "Data Source = (LocalDB)\\MSSQLLocalDB; Integrated Security = True; Connect Timeout = 30; "; 
    private string form1DatabasePath = "C:\\DbTemp"; 

    private void btnCreateDb_Click(object sender, EventArgs e) 
    { 
     string nameToCreate = cbxDb.Text; 
     SqlConnection myConn = new SqlConnection(form1ConnectionString); 

     string str = "CREATE DATABASE " +nameToCreate+ " ON PRIMARY " + 
      "(NAME = " +nameToCreate+ "_Data, " + 
      "FILENAME = '" +form1DatabasePath+ "\\" +nameToCreate+ ".mdf', " + 
      "SIZE = 4MB, MAXSIZE = 10MB, FILEGROWTH = 10%) " + 
      "LOG ON (NAME = " +nameToCreate+ "_Log, " + 
      "FILENAME = '" +form1DatabasePath+ "\\" +nameToCreate+ ".ldf', " + 
      "SIZE = 1MB, " + 
      "MAXSIZE = 5MB, " + 
      "FILEGROWTH = 10%)"; 

     SqlCommand myCommand = new SqlCommand(str, myConn); 

     try 
     { 
      myConn.Open(); 
      myCommand.ExecuteNonQuery(); 
      MessageBox.Show("DataBase '" + nameToCreate + "' was created successfully"); 
     } 
     catch (System.Exception ex) 
     { 
      MessageBox.Show("Exception in CreateDatabase " + ex.ToString(), "Exception in CreateDatabase", MessageBoxButtons.OK, MessageBoxIcon.Information); 
     } 
     finally 
     { 
      if (myConn.State == ConnectionState.Open) 
      { 
       myConn.Close(); 
      } 
     } 
    } 


    private void btnDeleteDb_Click(object sender, EventArgs e) 
    { 
     string nameToDelete = cbxDb.Text; 
     string myConnectionString = form1ConnectionString + "AttachDBFileName = " + form1DatabasePath + "\\" + nameToDelete + ".mdf "; 
     string str = "USE MASTER DROP DATABASE " + nameToDelete; 

      SqlConnection myConn = new SqlConnection(myConnectionString); 
      SqlCommand myCommand = new SqlCommand(str, myConn); 
      myConn.Open(); 

      try 
      { 
       myCommand.ExecuteNonQuery(); 
       MessageBox.Show("DataBase '" + nameToDelete + "' was deleted successfully"); 

      } 
      catch (System.Exception ex) 
      { 
       MessageBox.Show(ex.ToString(), "Exception in DeleteDatabase '" +nameToDelete+ "'", MessageBoxButtons.OK, MessageBoxIcon.Information); 
      } 
      finally 
      { 
       if (myConn.State == ConnectionState.Open) 
       { 
        myConn.Close(); 
       } 
      } 
    } 

    private void btnDoesDbExist_Click(object sender, EventArgs e) 
    { 
     string nameToTest = cbxDb.Text; 
     using (var connection = new SqlConnection(form1ConnectionString)) 
     { 
      using (var command = new SqlCommand(string.Format(
        "SELECT db_id('" +nameToTest+ "')", nameToTest), connection)) 
      { 
       connection.Open(); 

       if ((command.ExecuteScalar() != DBNull.Value)) 
       { 
        MessageBox.Show("DataBase '" +nameToTest+ "' exists"); 
       } 
       else 
       { 
        MessageBox.Show("Database '" +nameToTest+ "' does not exist"); 
       } 
      } 
     } 

    } 
} 

}

感謝所有的回覆，你的麻煩是極大的讚賞。

我現在明白我正在使用錯誤的數據庫，所以我嘗試使用SQL Server Compact來代替。已經卸載，再次下載，並重新安裝SQL Server Compact，包括SP1。也從https://visualstudiogallery.msdn.microsoft.com/0e313dfd-be80-4afb-b5e9-6e74d369f7a1下載並安裝了SQL Server Compact/SQLite Toolbox。但是，當我輸入using System.Data.SqlServerCe時，Visual Studio始終顯示錯誤。當我輸入SqlCeEngine或SqlCecommand時，我也出於同樣的原因。

在Visual Studio中，SQL Server Data Tools和SQL Server Compact & SQLite Toolbox顯示爲已安裝的產品，但未顯示爲SQL Server Compact。我是否需要將它安裝到Visual Studio中？如果是這樣，它是如何完成的？

Answer 1

如果該數據庫處於活動狀態，SQL Server不會讓您刪除數據庫的物理文件 - EVER。唯一你能做到這一點的是，如果數據庫是DETACHED（如前所述）

所以我懷疑你告訴我們的東西不是很正確？

我會改變你的「檢查數據庫存在」的邏輯是;

SELECT * FROM其中名稱=「yourdatabasename」

我就當你已經刪除了你的數據庫，只是爲了看看它返回反正運行此查詢sys.databases中。

Answer 2

在Solution Explorer下References，檢查是否列出了System.Data.SqlServerCe。如果沒有，請右鍵點擊References，然後點擊Add Reference→Browse按鈕並選擇文件System.Data.SqlServerCe.dll，可能在C:\Program Files\Microsoft SQL Server Compact Edition\v4.0\Desktop。 System.Data.SqlServerCe現在應該出現在References之下。

下面的程序似乎工作，而且更簡單。感謝所有的幫助。

using System; 
using System.Data; 
using System.Windows.Forms; 
//my additions 
using System.Data.SqlServerCe; 
using System.IO; 

namespace DataProg15 
{ 
    public partial class Form1 : Form 
    { 
     public Form1() 
     { 
      InitializeComponent(); 
     } 
     public static string form1DatabasePath = "C:\\DbTemp\\dbtemp1.sdf"; 
     public static string form1ConnectionString = "Data Source = " +form1DatabasePath; 

     private void btnCreateDb_Click(object sender, EventArgs e) 
     { 
       SqlCeEngine engine = new SqlCeEngine(form1ConnectionString); 
      try 
      { 
       engine.CreateDatabase(); 
       MessageBox.Show("DataBase '" +form1DatabasePath+ "' was created successfully"); 
      } 
      catch (System.Exception ex) 
      { 
       MessageBox.Show("Exception in CreateDatabase " + ex.ToString(), "Exception in CreateDatabase", MessageBoxButtons.OK, MessageBoxIcon.Information); 
      } 
      finally 
      { 
       engine.Dispose(); 
      } 
     } 

     private void btnDeleteDb_Click(object sender, EventArgs e) 
     { 
      if (File.Exists(form1DatabasePath)) 
      { 
       try 
       { 
        File.Delete(form1DatabasePath); 
        MessageBox.Show("DataBase '" +form1DatabasePath+ "' was deleted successfully"); 
       } 
       catch (System.Exception ex) 
       { 
        MessageBox.Show(ex.ToString(), "Exception in DeleteDatabase '" +form1DatabasePath+ "'", MessageBoxButtons.OK, MessageBoxIcon.Information); 
       } 
      } 
     } 

     private void btnDoesDbExist_Click(object sender, EventArgs e) 
     { 
      if (File.Exists(form1DatabasePath)) 
      { 
        MessageBox.Show("DataBase '" +form1DatabasePath+ "' exists"); 
      } 
      else 
      { 
        MessageBox.Show("DataBase '" +form1DatabasePath+ "' does not exist"); 
      } 
     } 
    } 
}