blocks|key|410514|text|那Math.Round(decimal+d,+int+decimals)呢？|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|410515|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/zy06z30k.aspx^0|1|Z|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

What about 
<a href="http://msdn.microsoft.com/en-us/library/zy06z30k.aspx" rel="noreferrer">Math.Round(decimal d, int decimals)</a>?

blocks|key|3254344|text|问题是-您是否真的需要以小数形式存储的精度，而不是仅将小数显示为所需的精度。大多数应用程序内部都知道它们希望达到多高的精确度，并显示到该精确度。例如，即使用户在帐号包中输入了100.00的发票，它仍然使用类似于val.ToString("n2")的东西打印为100。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3254345|3254346|如何从a创建b？如何从c创建b？|blockquote|3254347|3254348|3254349|C到B是可能的。|3254350|Console.WriteLine(Math.Round(2.00000000m,+1))+|code-block|syntax|javascript|3254351|生产2.0版|3254352|从a到b是很棘手的，因为引入精度的概念对数学来说有点陌生。|3254353|我猜一次可怕的黑客攻击可能是一次往返。|3254354|decimal+b+=+Decimal.Parse(a.ToString("#.0"));
Console.WriteLine(b);|3254355|3254356|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|10|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|11|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|12|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|14|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|15|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|16|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|18|8|@]|9|@]|A|$]]|$1|U|3|V|5|L|7|19|8|@]|9|@]|A|$M|N]]|$1|W|3|P|5|6|7|1A|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Y|$]]

The question is - do you really need the precision stored in the decimal, rather than just displaying the decimal to the required precision.
Most applications know internally how precise they want to be and display to that level of precision. For example, even if a user enters an invoice for 100 in an accounts package, it still prints out as 100.00 using something like val.ToString("n2"). 

<blockquote>
 How can I create b from a? How can I create b from c?
</blockquote>

c to b is possible.

<pre><code>Console.WriteLine(Math.Round(2.00000000m, 1)) 
</code></pre>

produces 2.0

a to b is tricky as the concept of introducing precision is a little alien to mathematics. 

I guess a horrible hack could be a round trip.

<pre><code>decimal b = Decimal.Parse(a.ToString("#.0"));
Console.WriteLine(b);
</code></pre>

produces 2.0

blocks|key|410546|text|我发现我可以通过乘以或除以一个花哨的1来“篡改”比例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410547|decimal+a+=+2m;
decimal+c+=+2.00000000m;
decimal+PreciseOne+=+1.000000000000000000000000000000m;
++//add+maximum+trailing+zeros+to+a
decimal+x+=+a+*+PreciseOne;
++//remove+all+trailing+zeros+from+c
decimal+y+=+c+/+PreciseOne;|code-block|syntax|javascript|410548|我可以构造一个足够精确的1来根据已知的大小改变比例因子。|410549|decimal+scaleFactorBase+=+1.0m;
decimal+scaleFactor+=+1m;
int+scaleFactorSize+=+3;

for+(int+i+=+0;+i+<+scaleFactorSize;+i%2B%2B)
{
++scaleFactor+*=+scaleFactorBase;
}

decimal+z+=+a+*+scaleFactor;|410550|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I found that I could "tamper" with the scale by multiplying or dividing by a fancy 1.

<pre><code>decimal a = 2m;
decimal c = 2.00000000m;
decimal PreciseOne = 1.000000000000000000000000000000m;
 //add maximum trailing zeros to a
decimal x = a * PreciseOne;
 //remove all trailing zeros from c
decimal y = c / PreciseOne;
</code></pre>

I can fabricate a sufficiently precise 1 to change scale factors by known sizes.

<pre><code>decimal scaleFactorBase = 1.0m;
decimal scaleFactor = 1m;
int scaleFactorSize = 3;

for (int i = 0; i &lt; scaleFactorSize; i++)
{
 scaleFactor *= scaleFactorBase;
}

decimal z = a * scaleFactor;
</code></pre>

blocks|key|413946|text|为了更严格地符合ECMA+CLI规范，在.NET+1.1中引入了类似于保留尾随零的功能。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|413947|在MSDN上有一些关于这方面的信息，例如here。|offset|length|413948|您可以按如下方式调整精度：|413949|413950|Math.Round+(或天花板、地板等)以降低精度(c中的b)|unordered-list-item|413951|乘以1.000...(使用您想要的小数位数)来提高精度-例如，乘以1.0M可以从a.|413952|得到b。|413953|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/aa289527(VS.71).aspx)^0|0|K|4|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@$D|Z|E|10|1|11]]|A|$]]|$1|F|3|G|5|6|7|12|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|I|3|J|5|K|7|14|8|@]|9|@]|A|$]]|$1|L|3|M|5|K|7|15|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|16|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]]]

Preserving trailing zeroes like this was introduced in .NET 1.1 for more strict conformance with the ECMA CLI specification.

There is some info on this on MSDN, e.g. <a href="http://msdn.microsoft.com/en-us/library/aa289527(VS.71).aspx" rel="noreferrer">here</a>.

You can adjust the precision as follows:

<ul>
<li>Math.Round (or Ceiling, Floor etc) to decrease precision (b from c)</li>
<li>Multiply by 1.000... (with the number of decimals you want) to increase precision - e.g. multiply by 1.0M to get b from a.</li>
</ul>

blocks|key|3467514|text|人们很容易混淆SQL+Server中的decimal和.NET中的decimal；它们是完全不同的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3467515|SQL+Server+decimal是一个定点数字，其精度和小数位数在定义列或变量时是固定的。|3467516|.NET+decimal是像float和double一样的浮点数(不同之处在于decimal准确地保留了十进制数，而float和double精确地保留了二进制数)。试图控制.NET+decimal的精度是没有意义的，因为无论是否存在填充零，所有计算都将产生相同的结果。|3467517|entityMap^0|J|7|X|7|0|B|7|0|5|7|E|5|K|6|13|7|1M|5|1S|6|2J|7|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|K|$]]

It's tempting to confuse <code>decimal</code> in SQL Server with <code>decimal</code> in .NET; they are quite different.

A SQL Server <code>decimal</code> is a fixed-point number whose precision and scale are fixed when the column or variable is defined.

A .NET <code>decimal</code> is a floating-point number like <code>float</code> and <code>double</code> (the difference being that <code>decimal</code> accurately preserves decimal digits whereas <code>float</code> and <code>double</code> accurately preserve binary digits). Attempting to control the precision of a .NET <code>decimal</code> is pointless, since all calculations will yield the same results regardless of the presence or absence of padding zeros.

blocks|key|410602|text|这将删除小数中所有尾随的零，然后您可以只使用ToString()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|410603|public+static+class+DecimalExtensions
{
++++public+static+Decimal+Normalize(this+Decimal+value)
++++{
++++++++return+value+/+1.000000000000000000000000000000000m;
++++}
}|code-block|syntax|javascript|410604|或者，如果您想要一个精确的尾随零的数量，例如5，首先Normalize()，然后乘以1.00000m。|410605|entityMap^0|M|A|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

This will remove all the trailing zeros from the decimal and then you can just use <code>ToString()</code>.

<pre><code>public static class DecimalExtensions
{
 public static Decimal Normalize(this Decimal value)
 {
 return value / 1.000000000000000000000000000000000m;
 }
}
</code></pre>

Or alternatively, if you want an exact number of trailing zeros, say 5, first Normalize() and then multiply by 1.00000m.

These lines in C#

<pre><code>decimal a = 2m;
decimal b = 2.0m;
decimal c = 2.00000000m;
decimal d = 2.000000000000000000000000000m;

Console.WriteLine(a);
Console.WriteLine(b);
Console.WriteLine(c);
Console.WriteLine(d);
</code></pre>

Generates this output:

<pre><code>2
2.0
2.00000000
2.000000000000000000000000000
</code></pre>

So I can see that creating a decimal variable from a literal allows me to control the precision.

<ul>
<li>Can I adjust the precision of decimal variables without using literals?</li>
<li>How can I create b from a? How can I create b from c? </li>
</ul>

Adjusting decimal precision, .net

SQL Server

C#中的这些行decimal a = 2m;decimal b = 2.0m;decimal c = 2.00000000m;decimal d = 2.000000000000000000000000000m;Console.WriteLine(a);Console.WriteLine(b);Console.Writ...

问调整小数精度，.net
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