在C＃中以编程方式创建本地数据库

Question

I am trying to create a wrapper class for creating a database.

I want the database to be created and destroyed in code by the use of create and delete functions.

I read online that using DROP DATABASE will destroy the database however I cannot check that I have interpreted the information correctly as I have been unable to write a create function.

The examples I have found are all for .mdf databases that include servers.

My database will be only used locally and will contain a single data table.

The database will be populated on creation by a data file chosen by the user.

Below is the class I have begun writing.

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.SqlServerCe;
using System.Windows.Forms;
using System.IO;

namespace DatabaseForm
{
    class DatabaseManager
    {

        private SqlCeConnection _sqlConnection;
        private string _cacheDatabase;
        private string _password;

        /// <summary>
        /// 
        /// </summary>
        public DatabaseManager()
        {
        }

        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        private string ConnectionString()
        {
            return string.Format("DataSource=\"{0}\"; Password='{1}'", this._cacheDatabase, this._password);
        }

        /// <summary>
        /// 
        /// </summary>
        private void Open()
        {
            if (_sqlConnection == null)
            {
                _sqlConnection = new SqlCeConnection(this.ConnectionString());
            }

            if (_sqlConnection.State == ConnectionState.Closed)
            {
                _sqlConnection.Open();
            }
        }

        /// <summary>
        /// 
        /// </summary>
        private void Close()
        {
            if (_sqlConnection != null)
            {
                if (_sqlConnection.State == ConnectionState.Open)
                {
                    _sqlConnection.Close();
                }
            }
        }

        /// <summary>
        /// 
        /// </summary>
        public void CreateDatabase(string dbname, string password)
        {
            string strCommand;
            try
            {
                Open();
                strCommand = "CREATE DATABASE " + dbname;
                SqlCeCommand sqlCommand = new SqlCeCommand(strCommand, _sqlConnection);
                sqlCommand.ExecuteNonQuery();
                Close();

                _cacheDatabase = new System.IO.FileInfo(System.Reflection.Assembly.GetExecutingAssembly().Location).DirectoryName + dbname;
                _password = password;
            }
            catch (Exception exc)
            {
                MessageBox.Show("Error in CreateDatabase(): " + exc.Message);
            }
        }

        /// <summary>
        /// 
        /// </summary>
        public void Delete()
        {
            string strCommand;
            try
            {
                Open();
                strCommand = "DROP DATABASE MyTable";
                SqlCeCommand sqlCommand = new SqlCeCommand(strCommand, _sqlConnection);
                sqlCommand.ExecuteNonQuery();
                Close();
            }
            catch (Exception exc)
            {
                MessageBox.Show("Error in Delete(): " + exc.Message);
            }
        }
    }
}

I want to get this working before I worry about how the class could fail. I will add defensive code at a later date.

So the area of issue is to do with the SqlCeConnection. What does the connection string need to be in order to create a database?

Once the database has been created I can use:

_cacheDatabase = new System.IO.FileInfo(System.Reflection.Assembly.GetExecutingAssembly().Location).DirectoryName + "\\MyDatabase.sdf";
_password = "";
string.Format("DataSource=\"{0}\"; Password='{1}'", _cacheDatabase, _password);

However MyDatabase.sdf does not exists until after CREATE DATABASE has been called.

Therefore what is the connection string?

Answer 1

Why bother with "DROP DATABASE". When using SQL Server CE, your database is one single file. It is enough to delete the file .

Answer 2

If you really want to DROP / CREATE a database like that then the easiest way to get the scripts right would be to create a sample database in the SQL Management Studio then right click on the database and select Tasks > Generate Scrips... .

There are plenty of options to choose and among them also a DROP / CREATE one. Then all you need to care is how to execute the scripts.