# 2023/11/08\_tableAndRowLock

由于锁 Monitor 是线程独占式访问的，所以其对性能的影响还是蛮大的，那有没有一种方式可是实现：允许多个线程同时读数据、只允许一个线程写数据呢

读写锁 ReaderWriterLockSlim 、就是 支持单个写线程和多个读线程的锁

```cs
using System;
using System.Collections.Generic;
using System.Threading;

public class LockExample
{
    private static ConcurrentDictionary<string, ReaderWriterLockSlim> tableLocks = new ConcurrentDictionary<string, ReaderWriterLockSlim>();
    private static ConcurrentDictionary<string, ReaderWriterLockSlim> rowLocks = new ConcurrentDictionary<string, ReaderWriterLockSlim>();

    public void LockTable(string tableName)
    {
        ReaderWriterLockSlim tableLock;

        lock (tableLocks)
        {
            if (!tableLocks.TryGetValue(tableName, out tableLock))
            {
                tableLock = new ReaderWriterLockSlim();
                tableLocks.Add(tableName, tableLock);
            }
        }

        tableLock.EnterWriteLock();
    }

    public void UnlockTable(string tableName)
    {
        ReaderWriterLockSlim tableLock;

        lock (tableLocks)
        {
            if (tableLocks.TryGetValue(tableName, out tableLock))
            {
                tableLock.ExitWriteLock();
            }
            else
            {
                Console.WriteLine("Table is not locked.");
            }
        }
    }

    public void LockRow(string rowId)
    {
        ReaderWriterLockSlim rowLock;

        lock (rowLocks)
        {
            if (!rowLocks.TryGetValue(rowId, out rowLock))
            {
                rowLock = new ReaderWriterLockSlim();
                rowLocks.Add(rowId, rowLock);
            }
        }

        rowLock.EnterWriteLock();
    }

    public void UnlockRow(string rowId)
    {
        ReaderWriterLockSlim rowLock;

        lock (rowLocks)
        {
            if (rowLocks.TryGetValue(rowId, out rowLock))
            {
                rowLock.ExitWriteLock();
            }
            else
            {
                Console.WriteLine("Row is not locked.");
            }
        }
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        LockExample lockExample = new LockExample();

        // 锁定表
        lockExample.LockTable("Products");

        // 锁定行
        lockExample.LockRow("1");

        // 解锁行
        lockExample.UnlockRow("1");

        // 解锁表
        lockExample.UnlockTable("Products");
    }
}

```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://note.lonelylty.com/coding/tableandrowlock.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.