azure-sdk-for-net
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Create example demonstrating combining expression filters for Table queries
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);
This was very helpful. Thank you!
@christothes should we include this in samples to make it more discoverable?
It's a pretty advanced scenario, so I think we should leave it here unless we get more feedback.