CODEWITHSUNDEEP
.netsqllinqlinq-to-sql
geemxx
geemxx

Reputation:

Obtain max length for a "string" column using LINQ to SQL

Is it possible to obtain the maximum column length for a VARCHAR, CHAR etc?

Upvotes: 6

Views: 11432

Answers (4)

Keith Barrows
Keith Barrows

Reputation: 25308

public static int GetLengthLimit(Model.RIVFeedsEntities ent, string table, string field)
{
    int maxLength = 0;   // default value = we can't determine the length

    // Connect to the meta data...
    MetadataWorkspace mw = ent.MetadataWorkspace;

    // Force a read of the model (just in case)...
    // http://thedatafarm.com/blog/data-access/quick-trick-for-forcing-metadataworkspace-itemcollections-to-load/
    var q = ent.Clients;
    string n = q.ToTraceString();

    // Get the items (tables, views, etc)...
    var items = mw.GetItems<EntityType>(DataSpace.SSpace);
    foreach (var i in items)
    {
        if (i.Name.Equals(table, StringComparison.CurrentCultureIgnoreCase))
        {
            // wrapped in try/catch for other data types that don't have a MaxLength...
            try
            {
                string val = i.Properties[field].TypeUsage.Facets["MaxLength"].Value.ToString();
                int.TryParse(val, out maxLength);
            }
            catch
            {
                maxLength = 0;
            }
            break;
        }
    }

    return maxLength;
}

Upvotes: 1

ctrlalt3nd
ctrlalt3nd

Reputation: 1362

Answered here:

Linq to SQL - Underlying Column Length

Though I found it neater to change:

public static int GetLengthLimit(Type type, string field) //definition changed so we no longer need the object reference
//Type type = obj.GetType(); //comment this line

And call using:

int i = GetLengthLimit(typeof(Pet), "Name");

Can anybody think of a of way to strongly type the field reference?

Upvotes: 1

mackenir
mackenir

Reputation: 10969

Here's a way which avoids touching the database:

  • Using Reflection, get the property of the entity class that corresponds to the column in question.
  • Then, retrieve the System.Data.Linq.Mapping.Column attribute of the property.
  • Then, parse the DbType property of this attribute (eg NVarChar(255) NOT NULL) to get the column length.

Upvotes: 4

TcKs
TcKs

Reputation: 26632

In pure T-SQL you can use this query:

select max_length from sys.columns as c inner join sys.objects o on c.object_id = o.object_id where o.name = 'myTable' and c.name = 'myColumn'

For linq-to-sql you need it rewrite into linq.

Upvotes: 1

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