C#如何使用数据库

数据库，在我们开发项目中那是最常见的了，无论复杂的项目、还是简单的项目，只要涉及数据的操作（增删改查），都会用到数据库。当然使用的数据库的种类根据项目的需求不同，也是不同的。在我所做的项目中就是用过ACCESS 2000、SQL Server 2000、Oracle 10g，因此简单总结下c#如何使用数据库的。程序执行sql语句（包括单条sql，多条sql，存储过程，函数等等）大体有三个步骤：连接数据库，执行sql语句，返回结果。那么我们来看看c#是如何完成这三个步骤的。无论哪种数据库都是这三个步骤，那么就不按数据库分了，按照返回结果的类型来分类吧。

数据库连接用的字符串：

即下面代码的connstr

"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="数据库路径";Persist Security Info=True;Jet OLEDB:Database Password="密码"

1、 执行sql语句返回受影响的行数

(1)、一条sql语句

public static int ExecuteNonQuery(string connStr, string sql)
{
OleDbConnection conn = null;
try
{
conn = new OleDbConnection(connStr);
conn.Open();
OleDbCommand command = new OleDbCommand(sql, conn);
return command.ExecuteNonQuery();
}
catch
{
return 0;
}
finally
{
if (conn != null)
conn.Close();
}
}

(2)、多条sql语句,返回受影响行数。由于多条sql为了保证数据库的正确性，最好使用事务方式运行。

public static int ExecuteNonQuery(string connStr, List<string> sqlList)
{
int executeCount = 0;

OleDbTransaction transaction = null;

OleDbConnection conn = null;
try
{
conn = new OleDbConnection(connStr);
conn.Open();

transaction = conn.BeginTransaction();

OleDbCommand command = new OleDbCommand();

command.Connection = conn;

command.Transaction = transaction;

for (int i = 0; i < sqlList.Count; i++)
{
command.CommandText = sqlList[i];

executeCount += command.ExecuteNonQuery();
}
transaction.Commit();
}
catch
{
if (transaction != null)
transaction.Rollback();
return 0;
}
finally
{
if (conn != null)
conn.Close();
}
return executeCount;
}

2、返回DataSet

public static DataSet ExecuteQueryReturnDataSet(string connStr, string sql)
{
OleDbConnection conn = null;
DataSet ds = null;
try
{
conn = new OleDbConnection(connStr);
ds = new DataSet();
conn.Open();

OleDbDataAdapter command = new OleDbDataAdapter(sql, conn);
command.Fill(ds, "datasetName");
}
catch
{
}
finally
{
if (conn != null)
conn.Close();
}
return ds;
}

3、返回OleDbDataReader

public static OleDbDataReader ExecuteQueryReturnReader(string sql, string connStr)
{
OleDbConnection conn = new OleDbConnection();
OleDbDataReader reader = null;

try
{
conn = new OleDbConnection(connStr);
conn.Open();

OleDbCommand command = conn.CreateCommand();
command.CommandText = sql;
reader = command.ExecuteReader();
}
catch
{
}
finally
{
if (conn != null)
conn.Close();
}
return reader;
}

4、执行存储过程并返回受影响行数(以Oracle为例)

public static int RunProcedure(string storedProcName, IDataParameter[] parameters)
{
int result = 0;
try
{
using (OracleConnection connection = new OracleConnection(GetConnectionString()))
{
connection.Open();

OracleCommand command = BuildQueryCommand(connection, storedProcName, parameters);

result = command.ExecuteNonQuery();
}
}
catch (Exception e)
{

}

return result;
}
private static OracleCommand BuildQueryCommand(OracleConnection connection, string storedProcName,

IDataParameter[] parameters)
{
OracleCommand command = new OracleCommand(storedProcName, connection);

command.CommandType = CommandType.StoredProcedure;

foreach (OracleParameter parameter in parameters)
{
command.Parameters.Add(parameter);
}

return command;
}

5、带参数的sql语句

public static int ExecuteNonQuery(string sql,string connStr, OleDbParameter[] commandParameters)
{
int count = 0;
OleDbCommand cmd = new OleDbCommand();

OleDbConnection conn = null;
try
{
conn = new OleDbConnection(connStr);
PrepareCommand(cmd, conn,sql, commandParameters);
count = cmd.ExecuteNonQuery();
cmd.Parameters.Clear();
}
catch

{
}
finally
{

if (conn != null)
{
conn.Close();
}
}
return count;
}

private static void PrepareCommand(OleDbCommand cmd, OleDbConnection conn, string sql, OleDbParameter[] cmdParms)
{
if (conn.State != ConnectionState.Open)
conn.Open();

cmd.Connection = conn;
cmd.CommandText = sql;
cmd.CommandType = CommandType.Text;

if (cmdParms != null)
{
foreach (OleDbParameter parm in cmdParms)
cmd.Parameters.Add(parm);
}
}

一般常用的就这么几种，数据库的几个重要对象分别是：OleDbCommand、OleDbConnection、OleDbDataReader、OleDbDataAdapter、DataSet。对于不同数据库，有几个对象需要对应相应数据库的对象。OleDbCommand、OleDbConnection、OleDbDataReader、OleDbDataAdapter,Oracle下OleDb换成Oracle，Sql Server下 则换成SQL。