Read values from a non-delimited string into class object

Question

I have a string with the following structure:

Student Name________AgeAddress_______________________Bithday___Lvl

Example:

Jonh Smith         016Some place in NY, USA               01/01/2014L01

As you can see, there is no delimited character like | or ,

Also, there is no space between fields (if you check, there is no space between Age/Address and Birthday/Level.

The size of each field is static so if data's length is less then it will contains white spaces.

I have a class that need to be filled with that information:

public class StudentData
{
    public char[] _name = new char[20];
    public string name;
    public char[] _age = new char[3];
    public string age;
    public char[] _address = new char[30];
    public string address;
    public char[] _bday = new char[10];
    public string bday;
    public char[] _level = new char[3];
    public string level;
}

Is there any way to do this automatically and dynamically?

I mean I really don't want to code like this:

myClass.name = stringLine.substring(0,19);
myClass.age = stringLine.substring(20,22);

That's because I have way more fields that the ones added in this example & way more string lines with other different data.

Update: There were supposed to be a lot of spaces between "Smith" and "016", but I don't know how to edit it.

Update2: If I use StringReader.Read() I can evade to use substring and indexes, but it isn't still so dynamically because I would need to repeat those 3 lines for each field.

StringReader reader = new StringReader(stringLine);
reader.Read(myClass._name, 0 myClass._name.Length);
myClass.name = new string(myClass._name);

Answer 1

Given your requirement I came up with an interesting solution. All be-it it may be more complex and longer than using the String.SubString() method as stated.

However this solution is transferable to other types and other string. I used a concept of Attributes, Properties, and Reflection to parse a string by a Fixed Length and setting the class Properties.

Note I did change your StudentData class to follow a more conventional coding style. Following this handy guide on MSDN: http://msdn.microsoft.com/en-us/library/xzf533w0(v=vs.71).aspx

Here is the new StudentData class. Note it uses the properties as opposed to fields. (Not discussed here).

public class StudentData
{
    string name;
    string age;
    string address;
    string bday;
    string level;

    [FixedLengthDelimeter(0, 20)]
    public string Name { get { return this.name; } set { this.name = value; } }

    [FixedLengthDelimeter(1, 3)]
    public string Age { get { return this.age; } set { this.age = value; } }

    [FixedLengthDelimeter(2, 30)]
    public string Address { get { return this.address; } set { this.address = value; } }

    [FixedLengthDelimeter(3, 10)]
    public string BDay { get { return this.bday; } set { this.bday = value; } }

    [FixedLengthDelimeter(4, 3)]
    public string Level { get { return this.level; } set { this.level = value; } }
}

Note on each of the properties there is an Attribute called FixedLengthDelimeter that takes two parameters.

1. OrderNumber
2. FixedLength

The OrderNumber parameter denotes the order in the string (not the position) but the order in which we process from the string. The second parameter denotes the Length of the string when parsing the string. Here is the full attribute class.

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public sealed class FixedLengthDelimeterAttribute : Attribute
{
    public FixedLengthDelimeterAttribute(int orderNumber, int fixedLength)
    {
        this.fixedLength = fixedLength;
        this.orderNumber = orderNumber;
    }

    readonly int fixedLength;

    readonly int orderNumber;

    public int FixedLength { get { return this.fixedLength; } }

    public int OrderNumber { get { return this.orderNumber; } }
}

Now the attribute is simple enough. Accepts the two paramters we discussed eariler in the constructor.

Finally there is another method to parse the string into the object type such as.

public static class FixedLengthFormatter
{
    public static T ParseString<T>(string inputString)
    {
        Type tType = typeof(T);
        var properties = tType.GetProperties(BindingFlags.Instance | BindingFlags.Public); //;.Where(x => x.GetCustomAttributes(typeof(FixedLengthDelimeterAttribute), false).Count() > 0);

        T newT = (T)Activator.CreateInstance(tType);

        Dictionary<PropertyInfo, FixedLengthDelimeterAttribute> dictionary = new Dictionary<PropertyInfo, FixedLengthDelimeterAttribute>();
        foreach (var property in properties)
        {
            var atts = property.GetCustomAttributes(typeof(FixedLengthDelimeterAttribute), false);
            if (atts.Length == 0)
                continue;
            dictionary[property] = atts[0] as FixedLengthDelimeterAttribute;
        }
        foreach (var kvp in dictionary.OrderBy(x => x.Value.OrderNumber))
        {
            int length = kvp.Value.FixedLength;
            if (inputString.Length < length)
                throw new Exception("error on attribute order number:" + kvp.Value.OrderNumber + " the string is too short.");
            string piece = inputString.Substring(0, length);
            inputString = inputString.Substring(length);
            kvp.Key.SetValue(newT, piece.Trim(), null);
        }
        return newT;
    }
}

The method above is what does the string parsing. It is a pretty basic utility that reads all the properties that have the FixedLengthDelimeter attribute applied a Dictionary. That dictionary is then enumerated (ordered by OrderNumber) and then calling the SubString() method twice on the input string.

The first substring is to parse the next Token while the second substring resets the inputString to start processing the next token.

Finally as it is parsing the string it is then applying the parsed string to the property of the class Type provided to the method.

Now this can be used simply like this:

string data1 = "Jonh Smith          016Some place in NY, USA         01/01/2014L01";
StudentData student = FixedLengthFormatter.ParseString<StudentData>(data1);

What this does:

• Parses a string against property attributes in a fixed length format.

What this does not do:

• It does convert the parsed strings to another type. Therefore all the properties must be a string. (this can be easily adapted by adding some type casting logic in).
• It is not well tested. This is only tested against a few samples.
• It is not by all means the only or best solution out there.

Answer 2

You could use FileHelpers library (NuGet).

Just define the structure of your input file with attributes:

[FixedLengthRecord]
public class StudentData
{
    [FieldFixedLength(20)]
    [FieldTrim(TrimMode.Right)] 
    public string name;
    [FieldFixedLength(3)]
    public string age;
    [FieldFixedLength(30)]
    [FieldTrim(TrimMode.Right)] 
    public string address;
    [FieldFixedLength(10)]
    public string bday;
    [FieldFixedLength(3)]
    public string level;
}

Then simply read the file using FileHelperEngine<T>:

var engine = new FileHelperEngine<StudentData>();
var students = engine.ReadFile(filename);