Including standard functions in search criteria

OData protocol supports standard functions that can be included in search criteria.

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Find a product with the given name coverted to a lowercase format

var x = ODataFilter.Expression;
var product = client
    .From("Products")
    .Filter(x.ProductName.ToLower() == "chai")
    .FindEntry();
Assert.Equal("Chai", product["ProductName"]);

Request URI: GET Products?$filter=tolower(ProductName)+eq+%27chai%27

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Find products with the length of name equal to 4

var x = ODataFilter.Expression;
var products = client
    .From("Products")
    .Filter(x.ProductName.Length() == 4)
    .FindEntries();
Assert.NotEmpty(products);

Request URI: GET Products?$filter=length(ProductName)+eq+4

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Find products with the name starting with the given string

var x = ODataFilter.Expression;
var products = client
    .From("Products")
    .Filter(x.ProductName.StartsWith("Ch") == true)
    .FindEntries();
Assert.NotEmpty(products);

Request URI: GET Products?$filter=startswith(ProductName%2c%27Ch%27)+eq+true

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Find products with the name containing the given string

var x = ODataFilter.Expression;
var products = client
    .From("Products")
    .Filter(x.ProductName.Contains("ai") == true)
    .FindEntries();
Assert.NotEmpty(products);

Request URI: GET Products?$filter=substringof(%27ai%27%2cProductName)+eq+true

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Find products with the name not containing the given string

var x = ODataFilter.Expression;
var products = client
    .From("Products")
    .Filter(x.ProductName.Contains("ai") == false)
    .FindEntries();
Assert.NotEmpty(products);

Request URI: GET Products?$filter=substringof(%27ai%27%2cProductName)+eq+false

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Find products with the name containing the given string at the specified position

var x = ODataFilter.Expression;
var products = client
    .From("Products")
    .Filter(x.ProductName.IndexOf("ai") == 2)
    .FindEntries();
Assert.NotEmpty(products);

Request URI: GET Products?$filter=indexof(ProductName%2c%27ai%27)+eq+2

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Alternative syntax for finding products with the name containing the given string at the specified position

var x = ODataFilter.Expression;
var products = client
    .From("Products")
    .Filter(x.ProductName.Substring(1) == "hai")
    .FindEntries();
Assert.NotEmpty(products);

Request URI: GET Products?$filter=substring(ProductName%2c1)+eq+%27hai%27

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See also:
Retrieving data
OData URI conventions