C#中的SQLCommand命令与DbTransaction事务处理

SqlConnection conn = new SqlConnection("server=10.126.64.11;user=it_oper;pwd=IT@SME2018;database=MESOtheata;");
conn.Open();
SqlCommand cmd = new SqlCommand("select * from [A_Emp_Dept_20190522]", conn);//    或者
                                                                             //或者    SqlCommand cmd=conn.CreateCommand();cmd.CommandText="";
SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);//读取完毕自动关闭连接
for (int i = 0; i < reader.FieldCount - 1; i++)
{
    Console.WriteLine(reader.GetName(i));//获取字段名
    while (reader.Read())//或者使用reader.HasRows属性判断时候有记录
    {
        Console.WriteLine(reader.GetDateTime(0).ToString());
        //或者 Console.WriteLine(Convert.ToDateTime(reader[0]).ToString());
        object[] values = new object[reader.FieldCount - 1];
        reader.GetValues(values);//读取一行所有字段的内容到Values字段中
        if (reader.IsDBNull(0)
        {
            //判断某字段是否为null值。
        }
    }

}
reader.Close();
//系统未关闭时，本Command更改CommandText后或新建Command还有继续使用此连接。
//conn.Close();

SqlCommand cmd = new SqlCommand("select * from [A_Emp_Dept_20190522] where  empname=@empname", conn);
SqlParameter para = new SqlParameter("@empname", SqlDbType.NVarChar, 10);
para.Value = "曾亮";
cmd.Parameters.Add(para);
//或者直接 cmd.Parameters.AddWithValue("@empname","曾亮");

OleDbCommand cmd = new OleDbCommand("select * from [A_Emp_Dept_20190522] where  empname like ?  and line like ?", conn);
cmd.Parameters.AddWithValue("@empname", "曾亮");
cmd.Parameters.AddWithValue("@line", "ODMZ%");//参加的参数的顺序应与？号的顺序相同，参数名可随意执行，甚至可以是空串。

SqlCommand cmd = new SqlCommand("update  [A_Emp_Dept_20190522] set dept='aa' where  dept='' ", conn);
int RecordAffected = cmd.ExecuteNonQuery();
if (RecordAffected == 0)
{
    Console.Write("操作失败");
}

SqlCommand cmd = new SqlCommand("select count(*) from   [A_Emp_Dept_20190522] ", conn);
if (Convert.ToInt32(cmd.ExecuteScalar()) == 0)//无记录，返回null
{
    Console.Write("无记录");
}

SqlTransaction trans = null;
try
{
    trans = conn.BeginTransaction();//默认事务隔离级别为ISolationLevel.Serilizable,oracle为ISolationLevel.ReadCommited
    SqlCommand cmd = new SqlCommand("Insert int **", conn);
    cmd.Transaction = trans;//为命令指定一个事务
    cmd.ExecuteNonQuery();
    //可以有多个SqlCommand一并执行，一起提交或回滚
    trans.Commit();
}
catch
{
    trans.Rollback();
}

SqlCommand cmd = new SqlCommand("GetCustomer", conn);
cmd.CommandType = CommandType.StoredProcedure;

SqlParameter para1 = new SqlParameter("@CustomerID", SqlDbType.NChar, 10);
para1.Value = "UINET";
cmd.Parameters.Add(para1);

SqlParameter para2 = new SqlParameter("@CompanyName", SqlDbType.NVarChar, 30);
para2.Direction = ParameterDirection.Output;
cmd.Parameters.Add(para2);

cmd.ExecuteNonQuery();
Console.WriteLine(cmd.Parameters["@CompanyName"].Value);

SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.SchemaOnly);//仅仅读取模式信息
DataTable table = reader.GetSchemaTable();
foreach (DataRow row in table.Rows)
{
    foreach (DataColumn col in table.Columns)
    {
        Console.WriteLine(col.ColumnName + row[col.ColumnName]);
    }
}

SqlCommand cmd = new SqlCommand("select * from CatoGories;select * from Customers", conn);

SqlDataReader reader = cmd.ExecuteReader();//仅仅读取模式信息
DataTable table = reader.GetSchemaTable();
do//首先自动定位在第一个结果集上
{
    while (reader.Read())
    {
        Console.Write(reader[0]);
    }
} while (reader.NextResult());