CODEWITHSUNDEEP
c#stringclass
Nate Pet
Nate Pet

Reputation: 46222

C# limit length of a string

I have the following class:

public class VendorClass {         
    public int VendorID { get; set; }
    public string VendorName { get; set; }
}

The fields above match fields in the database table. In the case of say VendorName, how do I give it a field width ?

VendorName maps to a field in the database which is varchar(15)

Upvotes: 3

Views: 14575

Answers (6)

MYV587
MYV587

Reputation: 1

I just met a problem like what you described and found a way to create a limited length's string. Maybe a little inflexible but concise when there are only finite varchar length definitions in database.

Firstly introduce some basic classes:

public class Length16
{
    public static int StringLength { get => 16; }
}

public class Length8
{
    public static int StringLength { get => 8; }
}

public class Length15
{
    public static int StringLength { get => 15; }
}

public class LimitedLengthString<T>
{
    private string _sValue;

    public LimitedLengthString(string sNewValue)
    {
        _sValue = sNewValue;
    }

    public static implicit operator LimitedLengthString<T>(string sNewValue)
    {
        var prop = typeof(T).GetProperty("StringLength");

        int iLength = (int)prop.GetValue(null);

        if (sNewValue.Length > iLength)
        {
            throw new Exception($"New string is too long! Allowed length {iLength}.");
        }

        return new LimitedLengthString<T>(sNewValue);
    }

    public static implicit operator string(LimitedLengthString<T> sSource)
    {
        return sSource.ToString();
    }

    public override string ToString()
    {
        return _sValue; 
    }
}

public class AutoTruncatedString<T>
{
    private string _sValue;

    public AutoTruncatedString(string sNewValue)
    {
        _sValue = sNewValue;
    }

    public static implicit operator AutoTruncatedString<T>(string sNewValue)
    {
        var prop = typeof(T).GetProperty("StringLength");

        int iLength = (int)prop.GetValue(null);

        return new AutoTruncatedString<T>(sNewValue.Substring(0, iLength));
    }

    public static implicit operator string(AutoTruncatedString<T> sSource)
    {
        return sSource.ToString();
    }

    public override string ToString()
    {
        return _sValue;
    }
}

Use them like this:

LimitedLengthString<Length8> sLimitedLength8;
sLimitedLength8 = "asdfgasdfg"; // will error out

AutoTruncatedString<Length8> sAutoTruncated8;
sAutoTruncated8 = "asdfgasdfg"; // will be truncated

sLimitedLength8 will throw an error if you try to assign a string longer than 8 and sAutoTruncated8 will truncate the string you assign to it.

For you, you can define the VendorName this way:

public LimitedLengthString<Length15> VendorName { get; set; }

Hope this could help you.

Upvotes: 0

Nasreddine
Nasreddine

Reputation: 37788

You can't limit the length of the string but you can use properties with backing fields to achieve the desired result :

public class VendorClass
{
    public int VendorID {  get; set; }

    private string _vendorName;

    public string VendorName
    {
        get { return _vendorName; }
        set
        {
            if (value.Length > 15)
            {
                _vendorName = value.Substring(0,15);                    
            } else { 
                _vendorName = value;
            }
        }
    }
}

Upvotes: 10

Xaisoft
Xaisoft

Reputation: 46591

I am not sure exactly what you are asking, but if you want to know the maximum length of a string, this question can help you.

If you want to limit the number of characters entered, I would suggest that you use server-side validation and/or client-side validation.

Upvotes: 0

Eric J.
Eric J.

Reputation: 150108

Strings in C# have almost-arbitrary length.

When loading from your database, it will automatically accommodate the actual string length. When saving to the database, your business logic, data layer or ORM (as appropriate) will need to ensure the proper maximum length.

Upvotes: 3

Daniel Casserly
Daniel Casserly

Reputation: 3543

I would question why you would do this in c# code. However this link has a couple of ways around this. I suppose either truncation or taking a subsring is the best option. You could also make sure that the UI (or the model-view) takes care of details such as this.

Upvotes: 0

BNL
BNL

Reputation: 7133

A string can't have a set length in C#. You will have to handle the db length through some other mechanism like validation. Can't really tell you more without more details.

Upvotes: 2

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