Method AssertCount

AssertCount<TSource>(IEnumerable<TSource>, int)

Asserts that a source sequence contains a given count of elements.

Declaration

public static IEnumerable<TSource> AssertCount<TSource>(this IEnumerable<TSource> source, int count)

Parameters

Type	Name	Description
IEnumerable<TSource>	source	Source sequence.
int	count	Count to assert.

Returns

Type	Description
IEnumerable<TSource>	Returns the original sequence as long it is contains the number of elements specified by count. Otherwise it throws ArgumentException.

Type Parameters

Name	Description
TSource	Type of elements in source sequence.

Remarks

The sequence length is evaluated lazily during the enumeration of the sequence.

Examples

The following code example demonstrates how to validate the length of a sequence using AssertCount.

var numbers = new string[] { "1", "2", "3", "4", "5", };

// Enumerate the sequence with a valid length.
// This code executes normally.
numbers
    .AssertCount(5)
    .Consume();

// Enumerate the sequence with an invalid length.
// This code throws an `ArgumentException`
try
{
    numbers
        .AssertCount(4)
        .Consume();
}
catch (ArgumentException ae)
{
    Console.WriteLine(ae.Message);

    // This code produces the following output:
    // Parameter "source.Count()" (int) must be equal to <4>, was <5>. (Parameter 'source.Count()')
}

Exceptions

Type	Condition
ArgumentNullException	source is null.
ArgumentOutOfRangeException	count is less than 0.
ArgumentException	Thrown lazily source has a length different than count.