Chapter 129: Using SQLite in C#

Section 129.1: Creating simple CRUD using SQLite in C#

First of all we need to add SQLite support to our application. There are two ways of doing that

Download DLL suiting your system from SQLite download page and then add to the project manually Add SQLite dependency via NuGet

We'll do it the second way

First open the NuGet menu

and search for System.Data.SQLite, select it and hit Install

Installation can also be done from Package Manager Console with

PM> Install-Package System.Data.SQLite

Or for only core features

PM> Install-Package System.Data.SQLite.Core

That's it for the download, so we can go right into coding.

First create a simple SQLite database with this table and add it as a file to the project

CREATE TABLE User(

Id INTEGER PRIMARY KEY AUTOINCREMENT, FirstName TEXT NOT NULL,

LastName TEXT NOT NULL

);

Also do not forget to set the Copy to Output Directory property of the file to Copy if newer of Copy always, based on your needs

Create a class called User, which will be the base entity for our database

private class User

{

public string FirstName { get; set; } public string Lastname { get; set; }

}

We'll write two methods for query execution, first one for inserting, updating or removing from database

private int ExecuteWrite(string query, Dictionary<string, object> args)

{

int numberOfRowsAffected;

//setup the connection to the database

using (var con = new SQLiteConnection("Data Source=test.db"))

{

con.Open();

//open a new command

using (var cmd = new SQLiteCommand(query, con))

{

//set the arguments given in the query foreach (var pair in args)

{

cmd.Parameters.AddWithValue(pair.Key, pair.Value);

}

//execute the query and get the number of row affected numberOfRowsAffected = cmd.ExecuteNonQuery();

}

return numberOfRowsAffected;

}

}

and the second one for reading from database

private DataTable Execute(string query)

{

if (string.IsNullOrEmpty(query.Trim())) return null;

using (var con = new SQLiteConnection("Data Source=test.db"))

{

con.Open();

using (var cmd = new SQLiteCommand(query, con))

{

foreach (KeyValuePair<string, object> entry in args)

{

cmd.Parameters.AddWithValue(entry.Key, entry.Value);

}

var da = new SQLiteDataAdapter(cmd);

var dt = new DataTable(); da.Fill(dt);

da.Dispose(); return dt;

}

}

}

Now lets get into our CRUD methods

Adding user

private int AddUser(User user)

{

const string query = "INSERT INTO User(FirstName, LastName) VALUES(@firstName, @lastName)";

//here we are setting the parameter values that will be actually //replaced in the query in Execute method

var args = new Dictionary<string, object>

{

{"@firstName", user.FirstName}, {"@lastName", user.Lastname}

};

return ExecuteWrite(query, args);

}

Editing user

private int EditUser(User user)

{

const string query = "UPDATE User SET FirstName = @firstName, LastName = @lastName WHERE Id = @id";

//here we are setting the parameter values that will be actually //replaced in the query in Execute method

var args = new Dictionary<string, object>

{

{"@id", user.Id}, {"@firstName", user.FirstName}, {"@lastName", user.Lastname}

};

return ExecuteWrite(query, args);

}

Deleting user

private int DeleteUser(User user)

{

const string query = "Delete from User WHERE Id = @id";

//here we are setting the parameter values that will be actually //replaced in the query in Execute method

var args = new Dictionary<string, object>

{

{"@id", user.Id}

};

return ExecuteWrite(query, args);

}

Getting user by Id

private User GetUserById(int id)

{

var query = "SELECT * FROM User WHERE Id = @id";

var args = new Dictionary<string, object>

{

{"@id", id}

};

DataTable dt = ExecuteRead(query, args);

if (dt == null || dt.Rows.Count == 0)

{

return null;

}

var user = new User

{

Id = Convert.ToInt32(dt.Rows[0]["Id"]),

FirstName = Convert.ToString(dt.Rows[0]["FirstName"]), Lastname = Convert.ToString(dt.Rows[0]["LastName"])

};

return user;

}

Section 129.2: Executing Query

using (SQLiteConnection conn = new SQLiteConnection(@"Data Source=data.db;Pooling=true;FailIfMissing=false"))

{

conn.Open();

using (SQLiteCommand cmd = new SQLiteCommand(conn))

{

cmd.CommandText = "query";

using (SqlDataReader dr = cmd.ExecuteReader())

{

while(dr.Read())

{

//do stuff

}

}

}

}

Note: Setting FailIfMissing to true creates the file data.db if missing. However, the file will be empty. So, any required tables have to be recreated.