Create example demonstrating combining expression filters for Table queries

[christothes]

Library name

Azure.Data.Tables

Please describe the feature.

See example here https://github.com/Azure/azure-sdk-for-net/issues/24033#issuecomment-927378891

Here are a couple examples of how to optionally combine some expressions as in your initial example:

If you want to deal just with expressions:

// Create the base expression
Expression<Func<MyEntity, bool>> query = e => e.PartitionKey == Partition;

// Create a variable for the expression body
var queryBody = query.Body;

// Create a variable for the expression parameter (MyEntity)
ParameterExpression parameter = query.Parameters[0];

if (startDate.HasValue)
{
    // Create the startDate filter
    Expression<Func<MyEntity, bool>> withStart = e => e.CreatedDate >= startDate.Value;

    // Combine this with the current queryBody
    queryBody = Expression.AndAlso(queryBody, withStart.Body);
}

if (endDate.HasValue)
{
    // Create the endDate filter
    Expression<Func<MyEntity, bool>> withEnd = e => e.CreatedDate <= endDate.Value;

    // Combine this with the current queryBody
    queryBody = Expression.AndAlso(queryBody, withEnd.Body);
}

// Create a new lambda with the current queryBody and our parameter
var lambda = Expression.Lambda<Func<MyEntity, bool>>(queryBody, parameter);

// Give the lambda to the Query method
client.Query(lambda);

Or if you want to do a bit of string management and avoid the complexity of expression manipulation:

// Get the oData string filter for your initial expression
string filter = TableClient.CreateQueryFilter<MyEntity>(e => e.PartitionKey == Partition);

if (startDate.HasValue)
{
    // Get the oData string filter for the startDate expression
    string withStart = TableClient.CreateQueryFilter<MyEntity>(e => e.CreatedDate >= startDate.Value);

    // Combine the two strings with an 'and'
    filter = $"({filter}) and ({withStart})";
}

if (endDate.HasValue)
{
    // Get the oData string filter for the endDate expression
    string withEnd = TableClient.CreateQueryFilter<MyEntity>(e => e.CreatedDate <= endDate.Value);

    // Combine the two strings with an 'and'
    filter = $"({filter}) and ({withEnd})";
}

// Give the filter string to the Query method
client.Query(filter);

[aproulx232]

This was very helpful. Thank you!

[pallavit]

@christothes should we include this in samples to make it more discoverable?

[christothes]

It's a pretty advanced scenario, so I think we should leave it here unless we get more feedback.