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Query


This method is used to query a row from the table.

Code Snippets

Below is the sample code to fetch a row from the [dbo].[Person] table.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query<Person>(10045).FirstOrDefault();
}

You can also query via expression.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query<Person>(e => e.Id == 10045).FirstOrDefault();
}

Or like below.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query<Person>(
        e => e.FirstName == "John" && e.LastName == "Doe").FirstOrDefault();
}

It always returns an IEnumerable<T> object even if your result is one.

Targeting a Table

You can also target a specific table by passing the literal table like below.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query<Person>("[dbo].[Person]",
        10045).FirstOrDefault();
}

Or via dynamics.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query("[dbo].[Person]",
        10045).FirstOrDefault();
}

The result is a list of dynamic objects of type ExpandoObject.

Specific Columns

You can also target a specific columns to be queried by passing the list of fields to be included in the fields argument.

using (var connection = new SqlConnection(connectionString))
{
    var fields = Field.Parse<Person>(e => new
    {
        e.Id,
        e.Name,
        e.DateOfBirth,
        e.DateInsertedUtc
    });
    var person = connection.Query<Person>(e => e.Id == 10045,
        fields: fields).FirstOrDefault();
}

Or via dynamics.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query("[dbo].[Person]",
        new { Id = 10045 },
        fields: Field.From("Id", "Name", "DateOfBirth", "DateInsertedUtc")).FirstOrDefault();
}

Type Result

You can also directly infer the resultset into a string type.

using (var connection = new SqlConnection(connectionString))
{
    var names = connection.Query<string>(ClassMappedNameCache.Get<Person>(),
        new QueryField("Name", Operation.Like, "%Anders%"),
        fields: Field.From(nameof(Person.Name))).FirstOrDefault();
}

Note: Inferrence works in all types but not from this operation. The other non-class type (i.e.: long, int, System.DateTime, etc) cannot be inferred as the TEntity generic type is filtered as class. Please see the ExecuteQuery operation for the support to the other types.

Table Hints

To pass a hint, simply write the table-hints and pass it in the hints argument.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query<Person>(10045,
        hints: "WITH (NOLOCK)").FirstOrDefault();
}

Or, you can use the SqlServerTableHints class.

using (var connection = new SqlConnection(connectionString))
{
    var person = connection.Query<Person>(10045,
        hints: SqlServerTableHints.TabLock).FirstOrDefault();
}

Ordering the Results

To order the results, you have to pass an array of OrderField objects in the orderBy argument.

using (var connection = new SqlConnection(connectionString))
{
    var orderBy = OrderField.Parse(new
    {
        LastName = Order.Descending,
        FirstName = Order.Ascending
    });
    var people = connection.Query<Person>(e => e.IsActive == true,
        orderBy: orderBy);
    // Do the stuffs for 'people' here
}

Filtering the Results

To filter the results, you have to pass a value at the top argument.

using (var connection = new SqlConnection(connectionString))
{
    var people = connection.Query<Person>(e => e.IsActive == true,
        top: 100);
    // Do the stuffs for 'people' here
}

Caching the Results

To cache the results, simply pass a literal string key into the cacheKey argument.

using (var connection = new SqlConnection(connectionString))
{
    var people = connection.Query<Person>(e => e.IsActive == true,
        cacheKey: "CackeKey:ActivePeople");
    // Do the stuffs for 'people' here
}

The cache expiration is defaulted to 180 minutes. You can override it by passing an integer value at the cacheExpirationInMinutes argument.