I use System.Data.SqlServer.SqlCeEngine() quite a lot in all my projects. I normally create the database on the fly when the application is launched for the first time and then I populate the initial data via a web service.
I often check if database objects exist before I create them. You can do this by querying the INFORMATION_SCHEMA views. I created a helper class called SqlCeEngineEx that contains the following methods for querying the INFORMATION_SCHEMA:
1) bool DoesTableExist(string table) - Checks if a table exists in the database
2) string[] GetTables() - Returns a string array of all the tables in the database
3) string[] GetTableConstraints(string table) - Returns a string array of all the constraints for a table
4) string[] GetTableConstraints() - Returns a string array of all the constraints in the database
And here is the full code:
public class SqlCeEngineEx : IDisposable
{
private SqlCeEngine engine;
public SqlCeEngineEx()
{
engine = new SqlCeEngine();
}
public SqlCeEngineEx(string connectionString)
{
engine = new SqlCeEngine(connectionString);
}
public bool DoesTableExist(string tablename)
{
bool result = false;
using (SqlCeConnection conn = new SqlCeConnection(LocalConnectionString)) {
conn.Open();
using (SqlCeCommand cmd = conn.CreateCommand()) {
cmd.CommandText =
@"SELECT COUNT(TABLE_NAME)
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME=@Name";
cmd.Parameters.AddWithValue("@Name", tablename);
result = Convert.ToBoolean(cmd.ExecuteScalar());
}
}
return result;
}
private string[] PopulateStringList(SqlCeCommand cmd)
{
List<string> list = new List<string>();
using (SqlCeDataReader reader = cmd.ExecuteReader()) {
while (reader.Read()) {
list.Add(reader.GetString(0));
}
}
return list.ToArray();
}
public string[] GetTables()
{
string[] tables;
using (SqlCeConnection conn = new SqlCeConnection(LocalConnectionString)) {
conn.Open();
using (SqlCeCommand cmd = conn.CreateCommand()) {
cmd.CommandText = "SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES";
tables = PopulateStringList(cmd);
}
}
return tables;
}
public string[] GetTableConstraints()
{
string[] constraints;
using (SqlCeConnection conn = new SqlCeConnection(LocalConnectionString)) {
conn.Open();
using (SqlCeCommand cmd = conn.CreateCommand()) {
cmd.CommandText = "SELECT CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS";
constraints = PopulateStringList(cmd);
}
}
return constraints;
}
public string[] GetTableConstraints(string tablename)
{
string[] constraints;
using (SqlCeConnection conn = new SqlCeConnection(LocalConnectionString)) {
conn.Open();
using (SqlCeCommand cmd = conn.CreateCommand()) {
cmd.CommandText =
@"SELECT CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE TABLE_NAME=@Name";
cmd.Parameters.AddWithValue("@Name", tablename);
constraints = PopulateStringList(cmd);
}
}
return constraints;
}
public string LocalConnectionString
{
get { return engine.LocalConnectionString; }
set { engine.LocalConnectionString = value; }
}
public void Compact()
{
engine.Compact(null);
}
public void Compact(string connectionString)
{
engine.Compact(connectionString);
}
public void CreateDatabase()
{
engine.CreateDatabase();
}
public void Repair(string connectionString, RepairOption options)
{
engine.Repair(connectionString, options);
}
public void Shrink()
{
engine.Shrink();
}
public bool Verify()
{
return engine.Verify();
}
public void Dispose()
{
engine.Dispose();
engine = null;
}
}
Wednesday, December 5, 2007
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