SQL et CSharp

Connection string

You can get the connection string from Visual Studio → View → SQL Server Object Explorer → Select a server → Properties → Connection string

Key	Description	Value
Data Source Server	nom ou adresse du serveur	(localdb)\MSSQLLocalDB tcp:my-server.database.windows.net,1433
Initial Catalog Database	nom de la bdd
Integrated Security Trusted_Connection		True, False
User ID		Domain\Username
Password	mot de passe de l'utilisateur
Application Name	se retrouve dans la colonne program_name de la table sys.dm_exec_sessions

Web.config

Web.config

<?xml version="1.0" encoding="utf-8"?> <configuration> <connectionStrings> <add name="MyConnectionString" connectionString="Server=MyServer; Database=MyDatabase; Trusted_Connection=True; MultipleActiveResultSets=true; Connection Timeout=3" providerName="System.Data.SqlClient" />

var connectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;

SqlConnectionStringBuilder

var connectionStringBuilder = new SqlConnectionStringBuilder(connectionString); connectionStringBuilder.ConnectionString = connectionString; string serverName = connectionStringBuilder.DataSource; string databaseName = connectionStringBuilder.InitialCatalog;

Select query

DataReader

Faster because it retries data as soon as it is available, and stores only one row at a time in memory, reducing system overhead.

var query = $"select top 1 * from MyTable"; using var sqlConnection = new SqlConnection(connectionString); await sqlConnection.OpenAsync(cancellationToken); using var cmd = new SqlCommand(query, sqlConnection); using var reader = await cmd.ExecuteReaderAsync(cancellationToken); var dataList = new List<Data>(); while (await reader.ReadAsync(cancellationToken)) { var data = new Data { Id = reader.GetFieldValue<int>("id"), Name = reader.GetFieldValue<string>("name") }; dataList.Add(data); }

DataAdapter

var query = $"select top 1 * from MyTable"; using var sqlConnection = new SqlConnection(connectionString); var dataAdapter = new SqlDataAdapter(query, sqlConnection); var dataTable = new DataTable(); sqlConnection.Open(); dataAdapter.Fill(dataTable);

ExecuteScalar

Reurns the first column of the first row in the result set, or a null reference if the result set is empty.

var query = $"select count(*) from MyTable"; using var sqlConnection = new SqlConnection(connectionString); using var sqlCmd = new SqlCommand(query, sqlConnection); sqlConnection.Open(); var count = sqlCmd.ExecuteScalar();

Insert query

var query = "insert into MyTable (Column1) values (@value1), (@value2)"; using var sqlConnection = new SqlConnection(connectionString); using var sqlCmd = new SqlCommand(cmd, sqlConnection); sqlCmd.Parameters.Add("@value1", SqlDbType.NVarChar, 50).Value = "Value1"; sqlCmd.Parameters.Add("@value2", SqlDbType.NVarChar, 50).Value = "Value2"; sqlConnection.Open(); sqlCmd.ExecuteNonQuery();

SqlBulkCopy

// TableLock: take bulk update locks on the destination table instead of row locks. // Avoid transaction deadlock on lock resources with other processes while running SqlBulkCopy in parallel. using var sqlBulkCopy = new SqlBulkCopy(connectionString, SqlBulkCopyOptions.TableLock);); sqlBulkCopy.BulkCopyTimeout = 0; // default: 60s, 0 → no limitation sqlBulkCopy.DestinationTableName = "[schema].[MyDestinationTable]"; // Add mappings so that the column order doesn't matter sqlBulkCopy.ColumnMappings.Add("SourceColumn1", "DestinationColumn1"); // with DbDataReader using var cmd = new OdbcCommand(query, odbcConnection); using var reader = await cmd.ExecuteReaderAsync(cancellationToken); await sqlBulkCopy.WriteToServerAsync(reader, cancellationToken); // with DataTable await sqlBulkCopy.WriteToServerAsync(sourceDataTable, cancellationToken);

Paramètres

L'utilisation de paramètres rend le code résistant aux injections de code SQL.

var cmd = "SELECT * FROM User WHERE UserName = @UserName AND Password = @Password"; using var sqlCmd = new SqlCommand(cmd); // Create the parameter objects as specific as possible. sqlCmd.Parameters.Add("@UserName", System.Data.SqlDbType.NVarChar, 50).Value = UserName; // avec DBNull sqlCmd.Parameters.Add("@UserName", System.Data.SqlDbType.NVarChar, 50).Value = (object)UserName ?? DBNull.Value;

Le nom de la table ne peut être passé en paramètre.

Insérer une liste d'éléments

var cmd = "insert into MaTable values (@id, @data1, @data2)"; using (var sqlConnection = new SqlConnection("ConnectionString")) { using (var sqlCmd = new SqlCommand(cmd, sqlConnection)) { try { sqlCmd.Parameters.Add("@id", System.Data.SqlDbType.Int); sqlCmd.Parameters.Add("@data1", System.Data.SqlDbType.Date); sqlCmd.Parameters.Add("@data2", System.Data.SqlDbType.TinyInt); sqlConnection.Open(); foreach (var element in elements) { sqlCmd.Parameters["@id"].Value = element.Id; sqlCmd.Parameters["@data1"].Value = element.Data1; sqlCmd.Parameters["@data2"].Value = element.Data2; sqlCmd.ExecuteNonQuery(); } } catch (SqlException ex) { }

SQLParameter

var parameters = new List<SqlParameter>(); parameters.Add(new SqlParameter(name, SqlDbType.Int) { Value = (object)myInt?.ToInt32(CultureInfo.InvariantCulture) ?? DBNull.Value }); parameters.Add(new SqlParameter(name, SqlDbType.Decimal) { Value = (object)myDecimal ?? DBNull.Value }); parameters.Add(new SqlParameter(name, SqlDbType.Bit) { Value = myBool.HasValue ? (object)(value.Value ? 1 : 0) : DBNull.Value }); parameters.Add(new SqlParameter(name, SqlDbType.Date) { Value = (object)myDate ?? DBNull.Value }); parameters.Add(new SqlParameter(name, SqlDbType.Char) { Value = (object)myString ?? DBNull.Value }); parameters.Add(new SqlParameter(name, SqlDbType.NVarChar) { Value = (object)myString ?? DBNull.Value }); // List<int> var idRecords = myListInt.Distinct().Select( id => { var record = new SqlDataRecord(new SqlMetaData("Id", SqlDbType.Int)); record.SetInt32(0, id); return record; }).ToList(); parameters.Add( new SqlParameter(name, SqlDbType.Structured) { TypeName = "schema.T_IdTable", Value = idRecords.Count > 0 ? idRecords : null }); // List<string> var nameRecords = value.Distinct().Select( name => { var record = new SqlDataRecord(new SqlMetaData("Name", SqlDbType.NVarChar, 50)); record.SetString(0, name); return record; }).ToList(); parameters.Add( new SqlParameter(name, SqlDbType.Structured) { TypeName = "schema.T_NameTable", Value = nameRecords.Count > 0 ? nameRecords: null }); var parameterNamesList = string.Join(", ", parameters.Select(p => p.ParameterName)); var storedProcedureResultRows = await dbContext.Database.SqlQuery<StoredProcedureResultRow>( $"{StoredProcedureName} {parameterNamesList}", parameters.Cast<object>().ToArray()).ToListAsync(cancellationToken);

User-Defined Table Type

SqlParameter et EF.

SqlCommand

ExecuteScalar

Exécute la requête et retourne la première colonne de la première ligne du jeu de résultats retourné par la requête.
Les colonnes ou lignes supplémentaires sont ignorées.

var cmd = "SELECT UserId FROM User WHERE UserName = Nicolas"; using (var sqlCmd = new SqlCommand(cmd)) { var userId = sqlCmd.ExecuteScalar(); }

ExecuteReader

var cmd = "SELECT * FROM table"; using(var sqlCmd = new SqlCommand(cmd, sqlConnection)) { sqlConnection.Open(); using(SqlDataReader sdr = sqlCmd.ExecuteReader()) { // liste des headers des colonnes var columns = Enumerable.Range(0, sdr.FieldCount).Select(sdr.GetName).ToList(); while (sdr.Read()) { var value = sdr["column name"] as string; var value = sdr["column name"] as int?; var value = (short)sdr["column name"]; // lance IndexOutOfRangeException si column name n'existe pas for (int i = 0; i < sdr.FieldCount; i++) { var columnName = sdr.GetName(i); var value = sdr.GetValue(i); } } } }

ExecuteNonQuery

string cmd = "INSERT INTO ma_table (colonne1, colonne2) VALUES (@param1, @param2)"; using (var sqlCmd = new SqlCommand(cmd, sqlConnection)) { sqlCmd.Parameters.Add("@param1", SqlDbType.NVarChar, 50).Value = "valeur1"; sqlCmd.Parameters.Add("@param2", SqlDbType.SmallInt, 1).Value = 0; // retourne le nombre de lignes affectées int nbOfAffectedRows = sqlCmd.ExecuteNonQuery(); }

Transaction

string cmd = "insert into MaTable (colonne1, colonne2) values (@param1, @param2)"; using (var sqlConnection = new SqlConnection(connectionString)) { sqlConnection.Open(); SqlTransaction txn = sqlConnection.BeginTransaction(); try { foreach (var element in MyCollection) { using (var sqlCmd = new SqlCommand(cmd, sqlConnection, txn)) { sqlCmd.Parameters.Add("@param1", SqlDbType.NVarChar, 50).Value = element.Property1; sqlCmd.Parameters.Add("@param2", SqlDbType.SmallInt, 1).Value = element.Property2; sqlCmd.ExecuteNonQuery(); } } txn.Commit(); } catch (Exception ex) { txn.Rollback(); } }

DataTable.Load

var dataTable = new DataTable(); var cmd = "SELECT * FROM ma_table;"; using(var sqlConnection = new SqlConnection(connectionString)) { using(var sqlCmd = new SqlCommand(cmd, sqlConnection)) { try { sqlConnection.Open(); using (var sdr = sqlCmd.ExecuteReader()) { dataTable.Load(sdr); } } catch (SqlException ex) { }

Mapping types TSQL et C#

TSQL type	C# type	Détails
bit	bool, bool?	1 → TRUE, 0 → FALSE
date datetime datetime2	DateTime, DateTime?	T-SQL date
tinyint	sbyte, sbyte? (SByte, SByte?)	1 Byte: -128 to 127
smallint	short, short? (Int16, Int16?)	2 Bytes: -2^15 (-32,768) to 2^15-1 (32,767)
int	int, int? (Int32, Int32?)	4 Bytes: -2^31 to 2^31-1
bigint	long, long? (Int64, Int64?)	8 Bytes: -2^63 to 2^63-1
decimal	decimal, decimal?
float	double, double?
nchar nvarchar	string, char[]
real	float, float? (Single, Single?)

Activer l'intégration CLR

sp_configure 'show advanced options', 1; GO RECONFIGURE; GO sp_configure 'clr enabled', 1; GO RECONFIGURE; GO -- test si l'intégration CLR est activée SELECT * FROM sys.configurations WHERE name = 'clr enabled' -- La colonne value doit avoir la valeur 1 IF NOT EXISTS (SELECT 1 FROM sys.configurations WHERE name = 'clr enabled' and value = 1) begin RAISERROR('CLR is NOT Enabled.',16,1) end GO

Exceptions

catch (SqlException ex) { foreach (SqlError error in ex.Errors) { string message = error.Message; } } catch (IndexOutOfRangeException ex) { // xxx n'est pas compris dans le select // ou si * est utilisé, xxx n'est pas une colonne de la table // sdr["xxx"] as string // ex.Message = "xxx" } catch (Exception ex) { }

Nuget package

Nuget package	Description
Microsoft.Data.SqlClient

Erreurs

string or binary data would be truncated

Ici c'est l'utilisation de quotes autour de @value1 et @value2 qui cause l'erreur.

string cmd = "INSERT INTO ma_table (param1, param2) VALUES ('@value1', '@value2')";