C＃/ TSQL小數邊界檢查 - 有更清晰的方法嗎？

Question

我寫了一個快速的c＃擴展方法，但不知道是否有更乾淨的方式來完成我想要做的事情。它確實有效，但是使用字符串轉發器感覺有點冒險，並插入一個小數。

目標是在應用程序級別，我們可以在發送到數據庫之前清除/修復任何數據問題以防止溢出。

注意：PCL庫，在這種情況下無法引用DLL的外部。

public static bool TsqlDecimalBoundariesCheck(this decimal valueToCheck, int precision, int scale) 
    { 
     if(scale > precision) throw new ArgumentException($"BOUNDARY CHECK: Scale [{scale}] must not be higher than Percision [{precision}]"); 

     // create X precision values of the value 9 
     var precisionValue = new string('9', precision); 

     // Insert the decimal place x positions from the right 
     if (scale > 0) 
     { 
      precisionValue = precisionValue.Insert((precision - scale), "."); 
     } 

     // Get the upper and lower values 
     var upperBoundry = decimal.Parse(precisionValue); 
     var lowerBoundry = upperBoundry * -1; 

     return (valueToCheck <= upperBoundry) && (valueToCheck >= lowerBoundry); 
    } 

而且一些快速的單元測試陪它：

[TestMethod] 
    public void TestBoundryConstraints() 
    { 
     var precision = 4; 
     var scale = 1; 

     var testValue = 1000m; 
     var result = testValue.TsqlDecimalBoundariesCheck(precision , scale); 
     Assert.IsFalse(result, $"Value {testValue} is expected to be outside Decimal({precision }, {scale})"); 

     testValue = -1000m; 
     result = testValue.TsqlDecimalBoundariesCheck(precision , scale); 
     Assert.IsFalse(result, $"Value {testValue} is expected to be outside Decimal({precision }, {scale})"); 

     testValue = 100m; 
     result = testValue.TsqlDecimalBoundariesCheck(precision , scale); 
     Assert.IsTrue(result, $"Value {testValue} is expected to be within Decimal({precision }, {scale})"); 

     testValue = 999.9m; 
     result = testValue.TsqlDecimalBoundariesCheck(precision , scale); 
     Assert.IsTrue(result, $"Value {testValue} is expected to be within Decimal({precision }, {scale})"); 

     testValue = -999.9m; 
     result = testValue.TsqlDecimalBoundariesCheck(precision , scale); 
     Assert.IsTrue(result, $"Value {testValue} is expected to be within Decimal({precision }, {scale})"); 
    } 

Answer 1

所以你絕對可以擺脫哈克字符串做(10^p - 1) * (10^-s)，讓您的上限和下限重複。

如果您想檢查以確保縮放不會被截斷，您可以實際上截斷它，然後比較值。如果截斷值和原始值相同，則比例有效。

全部放在一起，你會得到這樣的事情：

public static bool TsqlDecimalBoundariesCheck(this decimal valueToCheck, int precision, int scale) 
{ 
    if (scale > precision) throw new ArgumentException($"BOUNDARY CHECK: Scale [{scale}] must not be higher than Percision [{precision}]"); 

    //Upper/lower bounds 
    var step = (decimal)Math.Pow(10, precision); 
    var upperBoundry = (step - 1) * (decimal)Math.Pow(10, -scale); 
    var lowerBoundry = -1 * upperBoundry; 

    //Truncate decimal to scale 
    //If the truncated value does not equal the original, it must've been out of scale 
    step = (decimal)Math.Pow(10, scale); 
    var truncated = Math.Truncate(step * valueToCheck)/step; 

    return (valueToCheck <= upperBoundry) 
     && (valueToCheck >= lowerBoundry) 
     && truncated == valueToCheck; 
}