Question

我目前正在使用C＃编写应用程序并使用sqlite作为嵌入式数据库。我有我的应用程序在启动时创建一个新的数据库，但我如何让它检查数据库是否存在？如果它确实存在，我如何使用它，如果不存在如何创建新数据库？

这是我到目前为止所做的：

private void MainWindow_Loaded(object sender, EventArgs e)
{
    SQLiteConnection sqlite_conn;
    SQLiteCommand sqlite_cmd;
    bool newdb = false;
    if (newdb == true)
    {
        sqlite_conn = new SQLiteConnection("DataSource=database.db;Version=3;");
        sqlite_conn.Open();
        MessageBox.Show("31");
    }
    else
    {
        sqlite_conn = new SQLiteConnection("Data Source=database.db;Version=3;New=True;Compress=True;");
        sqlite_conn.Open();    
        sqlite_cmd = sqlite_conn.CreateCommand();    
        sqlite_cmd.CommandText = "CREATE TABLE Client (id integer primary key, Title  varchar(100),Name  varchar(100),Surname  varchar(100),Dateofbirth DateTime , Propertyname varchar(100),Moveindate DateTime,Relationship varchar(100),Spouse  varchar(100),Gender  varchar(100), spTitle  varchar(100),SpouseName  varchar(100),SpouseSurname  varchar(100),spDateofbirth DateTime ,spRelationship varchar(100),spSpouse  varchar(100),spGender  varchar(100));";
        sqlite_cmd.ExecuteNonQuery();
    }    
    sqlite_conn.Close();
    MessageBox.Show("dasdas");    
}

Answer 1

怎么样：

if(File.Exists("database.db"))

编辑：更改了原始代码中匹配来源的路径。

Answer 2

public async Task<bool> IsDbExists(string fileName)
    {
        try
        {
            var item = await ApplicationData.Current.LocalFolder.GetFileAsync(fileName);
            var db = new SQLiteConnection(DbHelper.DBPATH);
            var tb1 = db.GetTableInfo("Domain");
            var tb2 = db.GetTableInfo("Account");
            var tb3 = db.GetTableInfo("Product");
            var tb4 = db.GetTableInfo("Review");
            if (item == null || tb1.Count == 0 || tb2.Count == 0 || tb3.Count == 0 || tb4.Count == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        catch
        {
            return false;
        }
    }

This is one of the solution

Answer 3

    privat string _dataSource = @"H:\Ik.db";
    private SQLiteConnection _connection;
    private SQLiteCommand _command;

    private void connectToSQLite()
    {
        using (SQLiteConnection _connection = new SQLiteConnection())
        {
            if (File.Exists(@"H:\Ik.db"))
            {
                _connection.ConnectionString = $"Data Source={_dataSource};Version=3";
                _connection.Open();
                using (SQLiteCommand _command = new SQLiteCommand())
                {
                    _command.Connection = _connection;
                    _command.CommandText = "CREATE TABLE IF NOT EXISTS Kunden ( id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, Lastname VARCHAR(100) NOT NULL, " +
                     "name VARCHAR(100) NOT NULL, Code VARCHAR(100) NOT NULL, City VARCHAR(100) NOT NULL);";
                    try
                    {
                        _command.ExecuteNonQuery();
                        MessageBox.Show($"You Connected to local Data Base under {_dataSource} Sucssefuly");
                    }
                    catch (Exception)
                    {

                        throw;
                    }
                }
            }
            else
            {
                SQLiteConnection.CreateFile(@"H:\Ik.db");

            }
        }
    }

如何在SQLite中检查数据库是否存在C＃

3 个答案: