用nullable类型对数据库中datetime字段进行操作。
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string xddate1 = TextBox1.Text;
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DateTime? xddate2;
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if (xddate1.Length == 0)
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{
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xddate2 = null;
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}
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else
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{
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xddate2 = Convert.ToDateTime(xddate1);
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}
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table1里xddate字段设为可null。
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