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Gets or sets a string that specifies how to format the data on this column.
public string Format { get; set; }
The Format property affects how values are formatted for display, not the values stored internally. To retrieve the formatted value of a cell, use the GetDataDisplay(int, int) property.
The Format string has the same semantics as the format argument in the .NET Format(IFormatProvider, string, object) method. For details and a complete set of examples, see the .NET documentation.