Loops and string output

Question

Hi i have the following code:

static void CalcWordchange()
{
    List<string[]> l = new List<string[]>
        {
        new string[]{Question1, matcheditalian1},
        new string[]{"Sam", matcheditalian2},
        new string[]{"clozapine", matcheditalian3},
        new string[]{"flomax", matcheditalian4},
        new string[]{"toradol", matcheditalian5},
        };

    foreach (string[] a in l)
    {
        int cost = LevenshteinDistance.Compute(a[0], a[1]);
        errorString = String.Format("To change your input: \n {0} \n into the correct word: \n {1} \n you need to make: \n {2} changes \n ".Replace("\n",      Environment.NewLine),
            a[0],
            a[1],
            cost);
    }
}

Each time a button is clicked the text in the foreach loop runs and outputs a single sentence (the last item in the list). What i want to happen is to output all 5 items into a string.

I have added 4 new variables (errorString2, 3 etc) but cannot work out how to output it.

Any help is appreciated, Thanks

Ben Voigt · Accepted Answer · 2013-03-22 19:03:50Z

5

Try using a StringBuilder object to collect all the parts.

StringBuilder buildString = new StringBuilder();
foreach (string[] a in l)
{
    int cost = LevenshteinDistance.Compute(a[0], a[1]);
    buildString.AppendFormat("To change your input: \n {0} \n into the correct word: \n {1} \n you need to make: \n {2} changes \n ".Replace("\n",      Environment.NewLine),
        a[0],
        a[1],
        cost);
}
errorString = buildString.ToString();

answered Mar 22, 2013 at 19:03

Ben Voigt

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3 Comments

wjhguitarman Over a year ago

How does buildString.AppendLine differ from string += ? I'm assuming it is a better optimization in speed vs. the concatenation you referenced in my post?

Ben Voigt Over a year ago

@wjhguitarman: Yes. The string concatenation creates and throws away a bunch of temporary strings. StringBuilder preallocates a buffer and writes several items into it, then extends the buffer if it runs out. So both faster and uses less memory.

Tory Over a year ago

@wjhguitarman: String Concatenation creates a new string each time it is used (i.e. each pass through the loop), where as StringBuilder uses a self-growing char[] behind the scenes (until you call .ToString()). If that runs out of room, then StringBuilder will create a new array that is double the size of the old array. This means that it will take longer and longer for the array to need to be re-created, rather than one new string object every pass of the loop. String Concatination is still good for non-loops, especially if you are just adding 2-4 strings together.

wjhguitarman · Accepted Answer · 2013-03-22 19:01:50Z

2

Instead do something like this:

 string finalOuput = string.empty;
 foreach (string[] a in l)
 {
  int cost = levelshteinDstance.Compute(a[0], a[1]);
  finalOutput += string.Format("To change your input: \n {0} \n into the correct word: \n {1} \n you need to make: \n {2} changes \n ".Replace("\n",      Environment.NewLine),
            a[0],
            a[1],
            cost);
    }
}

//display finalOutput here

answered Mar 22, 2013 at 19:01

wjhguitarman

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1 Comment

Ben Voigt Over a year ago

Please don't recommend string concatentation in a loop.

Jim Mischel · Accepted Answer · 2013-03-22 19:04:16Z

1

Create a List<string> to hold the output:

var OutputList = new List<string>();
foreach (string[] a in l)
{
    errorString = ...
    OutputList.Add(errorString);
}

// output
foreach (var s in OutputList)
{
    Console.WriteLine(s);
}

Or you could use a StringBuilder:

var outputS = new StringBuilder();
foreach (string[] a in l)
{
    errorstring = ...
    outputS.AppendLine(errorString);
}

Console.WriteLine(outputS.ToString());

answered Mar 22, 2013 at 19:04

Jim Mischel

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