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如何使用VB.NET中可選參數(shù)調(diào)用方法
VB.NET可選參數(shù)的默認(rèn)值必須是一個(gè)常數(shù)表達(dá)式。
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過程定義中跟在可選參數(shù)后的每個(gè)參數(shù)也都必須是可選的。
下面的語法顯示帶VB.NET可選參數(shù)的過程聲明：
Sub sub name（ByVal parameter 1 As data type 1,
Optional ByVal parameter 2 As data type 2 = default value）
調(diào)用帶VB.NET可選參數(shù)的過程
過程在運(yùn)行時(shí)無法檢測到給定的參數(shù)是否已被省略，或者調(diào)用代碼是否已顯式提供默認(rèn)值。如果需要弄清楚這一點(diǎn)，可以設(shè)置一個(gè)不可能的值作為默認(rèn)值。下面的過程定義了可選參數(shù) office,并測試其默認(rèn)值 QJZ 以查看它在調(diào)用中是否已被省略：
Visual Basic
Sub notify（ByVal company As String, Optional ByVal office As String = "QJZ"）
If office = "QJZ" Then
Debug.WriteLine（"office not supplied -- using Headquarters"）
office = "Headquarters" End If
' Insert code to notify headquarters or specified office.
End Sub
如果可選參數(shù)是像 String 這樣的引用類型，只要它不是該變量所預(yù)期的值，就可以使用 Nothing 作為默認(rèn)值。
VB.NET可選參數(shù)和重載
定義帶可選參數(shù)的過程的另一種方法是使用重載。如果有一個(gè)可選參數(shù)，可以定義過程的兩個(gè)重載版本，一個(gè)接受此參數(shù)，另一個(gè)則不帶參數(shù)。此方法隨可選參數(shù)數(shù)目的增加而變得更復(fù)雜。然而，這樣做的優(yōu)點(diǎn)是可以完全確定調(diào)用程序是否提供了每個(gè)VB.NET可選參數(shù)。
求教啊求教，關(guān)于在VB.NET中不定項(xiàng)多條件查詢的難題
這個(gè)只能是一一判斷的：
為了敘述簡單，假設(shè)有兩個(gè)可選條件，內(nèi)容在： TextBox1(姓名)、TextBox2（部門）
主要是構(gòu)造 Sql的Where子句，那么：
Dim MySqlWhere As String
MySqlWhere=""
If TextBox1.Text"" Then
MySqlWhere= " Where 姓名 = '" TextBox1.Text "'"
End If
If TextBox2.Text"" Then
if MySqlWhere="" Then
MySqlWhere= " Where 部門 = '" TextBox1.Text "'"
Else
MySqlWhere= MySqlWhere " And 部門 = '" TextBox1.Text "'"
End If
End If
'如果還有第3，第4，那只能這樣了：
If TextBox3.Text"" Then
if MySqlWhere="" Then
MySqlWhere= " Where 字段3 = '" TextBox3.Text "'"
Else
MySqlWhere= MySqlWhere " And 字段3 = '" TextBox3.Text "'"
End If
End If
......
If TextBoxn.Text"" Then
if MySqlWhere="" Then
MySqlWhere= " Where 字段n = '" TextBoxn.Text "'"
Else
MySqlWhere= MySqlWhere " And 字段n = '" TextBoxn.Text "'"
End If
End If
注意：對于字符類型的字段，當(dāng)然要用單引號，上面那樣的，但是對于數(shù)值類型，就不要這個(gè)單引號的；但是對于日期類型，那么與字符類型不同的是，把前后的2個(gè)單引號，改為井號就是“#”， 這是很多初學(xué)者容易忽略的，也是很多教科書上不提的問題。
對于文本框，由于.NET不提供控件數(shù)組，但是還是可以用語句來實(shí)現(xiàn)類似數(shù)組的操作，這樣以上IF語句，就可以簡化。
tidesmile是什么意思？
首先沒有這個(gè)單詞
tide
n.
潮汐, 潮
潮流; 趨勢; 危機(jī)或危險(xiǎn)狀態(tài)
輪流升降或增減的事物
時(shí)期, 季節(jié)(多用于復(fù)合詞, 如:wintertide 冬季, eventide 黃昏)
(宗教上的)節(jié)期
at high [low] tide
處于高[低]潮
the tide of history
歷史的潮流
the tide of events
情勢
Christmas tide
圣誕節(jié)節(jié)期
Time and tide wait for no man.
[諺]歲月不等人; 天道不可抗。
習(xí)慣用語
attempt to go against the tide of history 倒行逆施
double tides 夜以繼日地(與動詞 work 連用) 狂怒地, 猛烈地(通常與動詞roar連用)
catch thetide 趁機(jī)
floodtide 漲潮;(事業(yè)、成就等的)頂點(diǎn),高峰
flowing tide 漲潮 正在增長、推進(jìn)的事物
full tide of pleasure 歡樂的絕頂
go [row] against the tide 反潮流, 排除俗見; 在逆境中工作
go with the tide 順應(yīng)潮流; 隨波逐流; 趕潮流
roll back the tide of war 擊退侵略
save the tide 趁漲潮進(jìn)出港口
stem thetide[current] 逆流而上 反潮流
swim with thetide 隨波逐流, 隨大流
tail to the tide (船只停泊中)隨潮起而掉頭
take the fortune at the tide (=take the tide at the flood) 及時(shí)利用時(shí)機(jī), 因利乘便
The tide turns. 形勢轉(zhuǎn)變, 局面改觀。
turn the tide 改變形勢, 改變局面使事態(tài)急轉(zhuǎn)直下
tide over [口](使)克服(困難), 使渡過(難關(guān)、危機(jī)等)
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現(xiàn)代英漢詞典tide
n.
潮水，潮汐
The tide is down.
潮退了。
At high tide the sea covers the rocks, but at low tide it uncovers them.
海水在高潮位時(shí)淹過了礁石，可是在低潮位時(shí)卻淹不過。
潮流；浪潮
詞性變化
vt.
tided, tiding
（與over連用）渡過（難關(guān)）
習(xí)慣用語
swim against the tide 反潮流；開倒車 (= go against the tide)
swim with the tide 順應(yīng)潮流，隨波逐流 (= go with the tide)
簡明英漢詞典tide
n.
潮, 潮汐, 潮流, 趨勢
柯林斯英語大詞典查詞歷史smiletidesmiletide
tide+{1}
[ta?d]
n
the cyclic rise and fall of sea level caused by the gravitational pull of the sun and moon. There are usually two high tides and two low tides in each lunar daySee tide-generating force See neap tide See spring tide
the current, ebb, or flow of water at a specified place resulting from these changes in level
the tide is coming in
See ebb See flood
a widespread tendency or movement
the tide of resentment against the government
a critical point in time; turning point
the tide of his fortunes
a fair or holiday
a season or time
Christmastide
any body of mobile water, such as a stream
a favourable opportunity
vb
to carry or be carried with or as if with the tide
to ebb and flow like the tide
tide
tide+{2}
[ta?d]
vb
to happen
柯林斯詞典說明
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WordNettide
tides tided tiding
Noun
1. the periodic rise and fall of the sea level under the gravitational pull of the moon
(hypernym) periodic event, recurrent event
(hyponym) high tide, high water, highwater
(part-meronym) tidal flow, tidal current
2. something that may increase or decrease (like the tides of the sea); "a rising tide of popular interest"
(hypernym) variation, fluctuation
(derivation) surge
3. there are usually two high and two low tides each day
(synonym) lunar time period
(hypernym) time period, period of time, period
Verb
1. rise or move foward; "surging waves"
(synonym) surge
(antonym) ebb, ebb away, ebb down, ebb out, ebb off
(hypernym) run, flow, feed, course
2. cause to float with the tide
(hypernym) float
(see-also) tide over, bridge over, keep going
3. be carried with the tide
(hypernym) float, drift, be adrift, blow
We agree to comply with the copyright notice and statements mentioned in WordNet license. 百科tide
詞性及解釋
n. 潮, 潮汐, 趨勢, 潮流, 漲潮, 高潮
vt. 使隨潮漂流
vi. 順潮行駛
更多解釋
相關(guān)詞條
ebb-tide tide staff neap tide tide curve dead tide spring tide earth tide superior tide tide energy low tide lee tide tide and half tide tide pool tide-rock half tide geomagnetic tide tide clock meteorological tide alkaline tide strain tide flood tide direct tide
該解釋由詞友提供，僅供參考。 免責(zé)聲明
與 tide 相關(guān)的例句East Scheldt Tide Lock
東斯海爾德?lián)醭遍l
equilibrium theory of tide
平衡潮學(xué)說
The tide flow in.
潮水急速涌了進(jìn)來。
The tide is in.
現(xiàn)在在漲潮。
The tide set in.
漲潮了。
A tide of immigration.
移民潮
It was high tide.
漲潮了。
The tide ebbed away.
潮水退下去了。
The tide has receded.
潮水退了。
The tide has turned.
現(xiàn)在潮流變了。
smile
vi.
微笑(at; on; upon)
譏[冷]笑(at)
眉開眼笑, 表示友好態(tài)度
變晴朗, 呈現(xiàn)樂觀氣象
He never smiles.
他從不露笑臉。
Who are you -ling at?
你在笑誰?
He smiled to see her so happy.
看到她這么高興, 他笑了。
習(xí)慣用語
be all smiles 笑容滿面, 喜氣洋洋
crack a smile [美口]面帶笑容
ghastly smile 慘笑
I should smile 我才不干呢; 我才不在乎呢 我很高興; 好得很
put a smile on sb.'s face 使某人高興[歡樂]
sardonic smile 嘲笑; 冷笑
(the) smiles of fortune 走運(yùn); 吉星高照
take the smiles off sb.'s face 使某人高興不下去; 使某人轉(zhuǎn)樂為苦
wipe the smiles off sb.'s face 使某人高興不下去; 使某人轉(zhuǎn)樂為苦
toothpaste smile [美口]牙膏廣告上露出皓齒的微笑
smile at 看著...微笑; 一笑置之
smile away 以微笑消除; 笑著忘掉
smile on 向...微笑
smile upon 向...微笑
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現(xiàn)代英漢詞典smile
vi., vt.
smiled, smiling
微笑；露出微笑
She smiled when she saw me.
她看見我時(shí)露出微笑。
"At the station, he was told by a smiling policeman that his bicycle had been found."
"在警察局里,一個(gè)滿面笑容的警察告訴他,他的自行車找到了。"
呈喜色；顯出好意
Fortune has always smiled at him.
他的命運(yùn)一向很好。
（與on, upon連用）贊許，鼓勵(lì)
詞性變化
n.
微笑，笑容
a smile on his face
他臉上的笑容
簡明英漢詞典smile
vi.
(～ at) 微笑
n.
微笑
柯林斯英語大詞典查詞歷史tidetidesmilesmile
[sma?l]
n
a facial expression characterized by an upturning of the corners of the mouth, usually showing amusement, friendliness, etc, but sometimes scorn, etc
favour or blessing
the smile of fortune
an agreeable appearance
vb
to wear or assume a smile
to look (at) with a kindly or amused expression.to look derisively (at) instead of being annoyed.to bear (troubles, etc) patiently
to show approval; bestow a blessing
to express by means of a smile
she smiled a welcome
to drive away or change by smiling
smile away one's tears
習(xí)慣用語
come up smiling to recover cheerfully from misfortune
柯林斯詞典說明
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WordNetsmile
smiles smiled smiling
Noun
1. a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement
(synonym) smiling, grin, grinning
(hypernym) facial expression, facial gesture
(hyponym) smirk
Verb
1. change one's facial expression by spreading the lips, often to signal pleasure
(hypernym) grimace, make a face, pull a face
(hyponym) dimple
(derivation) smiling, grin, grinning
2. express with a smile; "She smiled her thanks"
(hypernym) express, show, evince
(derivation) smiling, grin, grinning
We agree to comply with the copyright notice and statements mentioned in WordNet license.
同義詞： beam chuckle grin laugh smirk
反義詞： frown
百科smile
詞性及解釋
n. 微笑, 喜色, 笑容
vi. 微笑, 覺得好笑
vt. 微笑著表示
更多解釋
相關(guān)詞條
smile on sardonic smile ghastly smile smile upon smile away smile at I should smile crack a smile an artificial smile a ghost of a smile smile on sb Hanes-Whistle-Smile sign
該解釋由詞友提供，僅供參考。 免責(zé)聲明
與 smile 相關(guān)的例句A manmay smile and smile and be villain.
笑里藏奸。
His smile disarmed us.
他的微笑消除了我們的怒氣。
A motherlike smile, embrace
慈母般的微笑、擁抱
a sickening sanctimonious smile.
令人作嘔的偽裝神圣的笑容。
A vague smile, gesture
用意不明的微笑、手勢
A villainous plot, smile
邪惡的陰謀、猙獰的笑
Always wears a smile.
總是面露微笑
He forced a smile.
他強(qiáng)作笑顏。
He wore a smile.
他面帶笑容。
Here comes that smile!
那種微笑又來啦！
VB.Net中的Or是什么意思？
在邏輯運(yùn)算中表示 或者
稱作邏輯或
用法 if 1 or 0 then print 111
分享題目：包含orvb.net的詞條
轉(zhuǎn)載源于：http://www.dlmjj.cn/article/dogeheg.html
