Entity Framework Tutorial 1 - Single | SingleOrDefault | First | FirstOrDefault
EF Core Method Comparison
Method | Description | Throws Exception | Returns Null | Use Case |
---|---|---|---|---|
Single |
Returns the only element of a sequence, and throws an exception if there is not exactly one element. | If no elements or more than one element are found. | Never | When exactly one element is expected in the result set, and any deviation is an error condition. |
SingleOrDefault |
Returns the only element of a sequence, or a default value if the sequence is empty. Throws an exception if there is more than one element. | If more than one element is found. | If no elements are found. | When zero or one element is expected. More than one element is considered an error condition. |
First |
Returns the first element of a sequence. Throws an exception if no elements are found. | If no elements are found. | Never | When at least one element is expected, and only the first element is needed. |
FirstOrDefault |
Returns the first element of a sequence, or a default value if the sequence is empty. | Never | If no elements are found. | When zero or more elements are expected, and only the first element is needed. |
Examples:
Single:
var item = dbContext.Items.Single(i => i.Id == 1);
// Throws InvalidOperationException if no item or more than one item with Id == 1.
SingleOrDefault:
var item = dbContext.Items.SingleOrDefault(i => i.Id == 1);
// Throws InvalidOperationException if more than one item with Id == 1.
// Returns null if no item with Id == 1.
First:
var item = dbContext.Items.First(i => i.Id == 1);
// Throws InvalidOperationException if no item with Id == 1.
FirstOrDefault:
var item = dbContext.Items.FirstOrDefault(i => i.Id == 1);
// Returns null if no item with Id == 1.
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