企业官网建设流程全解析

一、字典、哈希表

同样是读取txt文本，为什么要使用字典哈希表，不使用数组呢？
时间复杂度不同。数组遍历的时间复杂度O(n)，哈希表时间复杂度O(1)

二、字典的具体实现

'''<summary>''' 从字典中读取 Double 值，键不存在或解析失败时返回默认值'''</summary>Private Shared FunctionGetDouble(dict AsDictionary(Of String,String),key As String,defaultVal As Double)As Double Dim val As String=Nothing If Not dict.TryGetValue(key,val)Then Return defaultVal Dim result As Double If Double.TryParse(val,NumberStyles.Float,CultureInfo.InvariantCulture,result)Then Return result Return defaultVal End Function'''<summary>''' 从字典中读取可空 Double 值，键不存在或值为空时返回 Nothing'''</summary>Private Shared FunctionGetNullableDouble(dict AsDictionary(Of String,String),key As String)As Double?Dim val As String=Nothing If Not dict.TryGetValue(key,val)Then Return Nothing If String.IsNullOrEmpty(val)Then Return Nothing Dim result As Double If Double.TryParse(val,NumberStyles.Float,CultureInfo.InvariantCulture,result)Then Return result Return Nothing End Function'''<summary>''' 从字典中读取 Integer 值，键不存在或解析失败时返回默认值'''</summary>Private Shared FunctionGetInt(dict AsDictionary(Of String,String),key As String,defaultVal As Integer)As Integer Dim val As String=Nothing If Not dict.TryGetValue(key,val)Then Return defaultVal Dim result As Integer If Integer.TryParse(val,NumberStyles.Integer,CultureInfo.InvariantCulture,result)Then Return result Return defaultVal End Function'''<summary>''' 从字典中读取枚举值，键不存在或解析失败时返回默认值'''</summary>Private Shared FunctionGetEnum(Of T As Structure)(dict AsDictionary(Of String,String),key As String,defaultVal As T)As T Dim val As String=Nothing If Not dict.TryGetValue(key,val)Then Return defaultVal Dim result As T=Nothing If[Enum].TryParse(Of T)(val,True,result)Then Return result Return defaultVal End Function