DataTable.Merge的内部实现

DataTable.Merge

internal void MergeTable(DataTable src)
{
    bool enforceConstraints = false;
    if (!this.isStandAlonetable)
    {
        if (src.DataSet == this.dataSet)
        {
            return;
        }
        enforceConstraints = this.dataSet.EnforceConstraints;
        this.dataSet.EnforceConstraints = false;
    }
    else
    {
        if (src == this.dataTable)
        {
            return;
        }
        this.dataTable.SuspendEnforceConstraints = true;
    }
    if (this.dataSet != null)
    {
        if ((src.DataSet == null) || (src.DataSet.namespaceURI != this.dataSet.namespaceURI))
        {
            this._IgnoreNSforTableLookup = true;
        }
    }
    else if (((this.dataTable.DataSet == null) || (src.DataSet == null)) || (src.DataSet.namespaceURI != this.dataTable.DataSet.namespaceURI))
    {
        this._IgnoreNSforTableLookup = true;
    }
    this.MergeTableData(src);
    DataTable dataTable = this.dataTable;
    if ((dataTable == null) && (this.dataSet != null))
    {
        if (this._IgnoreNSforTableLookup)
        {
            dataTable = this.dataSet.Tables[src.TableName];
        }
        else
        {
            dataTable = this.dataSet.Tables[src.TableName, src.Namespace];
        }
    }
    if (dataTable != null)
    {
        dataTable.EvaluateExpressions();
    }
    if (!this.isStandAlonetable)
    {
        this.dataSet.EnforceConstraints = enforceConstraints;
    }
    else
    {
        this.dataTable.SuspendEnforceConstraints = false;
        try
        {
            if (this.dataTable.EnforceConstraints)
            {
                this.dataTable.EnableConstraints();
            }
        }
        catch (ConstraintException)
        {
            if (this.dataTable.DataSet != null)
            {
                this.dataTable.DataSet.EnforceConstraints = false;
            }
            throw;
        }
    }
}