How can I convert Bigint value which produced with Timespan?

TimeSpan ts = new TimeSpan(bigintvalue);

It is not clear from your post what the scale of your bigint value is, but the scale for the value to the TimeSpan constructor is 100 ns, so you may have to multiply or divide to the correct scale.

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Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se